UNIVERSITY OF ILLINOIS BULLETIN 

Issued Weekly 

Vol. XVI May 26, 1919 No. 39 

£!ntered as second-class matter December 11, 1919, at the post office at Urbana, Illinois, under the Act of Aucust 
24, 1912. Acceptance for mailing at the special rate of postage provided for in section 1103, 

Act of October 3, 1917, authorised July 31, 1918] 


PANEL SYSTEM OF COAL MININO 
A GRAPHICAL STUDY OP PERCENTAGE 

OF EXTRACTION 

BY 

C. M. YOUNG 

Illinois Coal Mining Investigations Cooperative Agreement 

(This Report was prepared under a CoSperative Agreement between the 
Engineering Experiment Station op the University op Illinois, 

THE Illinois State Geological Survey, and 
the U. S. Bureau op mines) 



Ettropban Agent 
Chapman & Hall, Ltd., London 











T he Engineering Experiment Station was established by act of 
the Board of Trustees, December 8, 1903. It is the purpose 
of the Station to carry on investigations along various lines 
of engineering and to study problems of importance to professional 
engineers and to the manufacturing, railway, mining, constructional, 
and industrial interests of the State. 

The control of the Engineering Experiment Station is vested in 
the heads of the several departments of the College of Engineering. 
These constitute the Station Staff and, with the Director, determine 
the character of the investigations to be undertaken. The work is 
carried on under the supervision of the Staff, sometimes by research 
fellows as graduate work, sometimes by members of the instructional 
staff of the College of Engineering, but more frequently by investi¬ 
gators belonging to the Station corps. 

The volume and number at the top of the front cover page are 
merely arbitrary numbers and refer to the general publications of 
the University of Illinois; either above the title or below the seal is 
given the number of the Engineering Experiment Station bulletin 
or circular which should be used in referring to these publications. 

The present bulletin is issued under a cooperative agreement 
between the Engineering Experiment Station of the University of 
Illinois, the State Geological Survey, and the United States Bureau 
of Mines. The reports of this cooperative investigation are issued 
in the form of bulletins by the Engineering Experiment Station, the 
State Geological Survey and the United States Bureau of Jilines. 
For bulletins issued by the Engineering Experiment Station, address 
Engineering Experiment Station, Urbana, Illinois; for those issued 
by the State Geological Survey, address State Geological Survey, 
Urbana, Illinois; and for those issued by the United States Bureau 
of Mines, address the Director, United States Bureau of Mines, Wash¬ 
ington, D. C. 


UNIVERSITY OF ILLINOIS 
ENGINEERING EXPERIMENT STATION 


Bulletin No. 113 


M.4Y, 1919 


PANEL SYSTEM OF COAL MINING 
A GRAPHICAL STUDY OF PERCENTAGE 

OF EXTRACTION 


- 

C.M. YOUNG 

Assistant Professor of Mining Rese.arch 


ENGINEERING EXPERIMENT STATION 

Published by the University of Illinois, Urbana 













«f i). 

*6 1920 



5 


) 



J 


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f 


1 









CONTENTS 


-r T PAGE 

i. Introduction •. 7 

1. Reasons for the Investigation.7 

2. Other Investigations.7 

3. Acknowledgments. . . 7 

4. Summary. 7 

5. Reasons for Low Extraction.8 

II. Advantages of Greater Extraction.11 

6. Investment per Ton of Total Output.11 

7. Cost of Haulage.11 

8. Cost of Ventilation.11 

9. Efficiency of Supervision.12 

10. Prevention of AVaste.12 

[II. Principles Involved in High Extraction.13 

IV. Method of Investigating the Percentage of Extraction 15 

11. Basis of Calculation.15 

12. Method of Computation v.16 

13. Method of Procedure . . . .18 

14. Lengths of Entries . . . ' . . *.21 

15. Percentage of Extraction in Entries.21 

16. Percentage of Extraction Inside the Panel ... 22 


17. Percentage of the Total Area Occupied by Panels 22 

18. Percentage of Total Area Extracted in All Panels 23 

19. Entry Area Outside the Panels.23 

20. Percentage of Area Occupied by Entries ... 24 

21. Percentage of Total Area Extracted in Entries . . 24 

22. Summary of Percentages, of Extraction .... 24 

23. Area Left in Pillars Outside the Panels .... 25 

24. Percentages of Extraction with Different Room 

Widths.. . 26 

25. Tables and Diagrams.27 

26. Other Methods of Computation.43 

Appendix I. Cost of Production and the Percentage of 

Extraction in Fulton County .... 

Appendix II. Extraction at Dewmaine ....... 66 

Appendix III. Work of J. C. Gibson .70 


3 

























LIST OF FIGUEES 


NO. 

1 . 

2 . 

3. 

4. 


o. 


6 . 

7. 

8 . 

9. 

10 . 

11 . 

12 . 

13. 


14. 

15. 

16. 

17. 

18. 
19. 


20 . 


PAGE 

Map of 160-Acre Tract Selected for Investigation.17 

Eoom Entry and Eoom Necks.20 

Percentage of Extraction Inside the Panel for Eooms 250 Feet Long, 25 

Feet Wide, on 50-Foot Centers.28 

Percentage of Total Area Included in Panels For Eooms 25 Feet Wide, 

on 50-Foot Centers.SO 

Percentage of Total Area Occupied by Entries for Eooms 25 Feet Wide, 

on 50-Foot Centers.32 


Total Percentage of Extraction.35 

Distribution of Extraction and Loss for Eooms 200 Feet Long, 25 Feet 

Wide, on 50-Foot Centers. 40 

Distribution of Extraction and Loss for Eooms 250 Feet Long, 25 Feet 

Wide, on 50-Foot Centers.1 

Distribution of Extraction and Loss for Eooms 300 Feet Long, 25 Feet 

Wide, oh 50-Foot Centers.42 

Unit Panel.44 

Map of 160 Acres for J. C. Quade’s Computation.47 

Number of Eooms per Entry, Coal per Eoom, Total Coal from 160 Acres, 
Percentage of Area Excavated, Cost per 1000 Tons, Saving per 1000 
Tons.56 

Number of Eooms per Entry, Coal per Eoom, Total Coal from 160 Acres, 
Percentage of Area Excavated, Cost per 1000 Tons, Saving per 

1000 Tons.57 

Production from Eooms, Entries, and from Additional Cross-Cut Width 60 
Summary of Costs and Output for Eooms 24 Feet Wide and 210 Feet 

Long.61 

Effect of Changes in Cross-Cut Width on Cost of Cross-Cuts and Coal Pro¬ 
duced .62 

Certain Fixed Charges per 1000 Tons, Saving per 1000 Tons, Total Out¬ 
put from 160 Acres.63 

Summation of Fixed Charges and Output for 160 Acres.64 

Dimensions of Eooms and Cross Entries at Dewmaine.66 

Portion of Mine as Mapped by J. C. Gibson.71 


4 

















LIST OF TABLES 

NO. PAGE 

1. Extraction in Panels.28 

2. Extraction in Entries.31 

3. Length of Entries and Yards of Narrow Work.33 

4. Percentage of Extraction in Panels, in Entries, and Total Extraction . 34 

5. Percentage Lost in Panels.37 

6. Percentage Lost in Pillars Outside the Panels Except in Entries . 

7. Extraction in Wide Work and in Narrow Work.38 

8. Number of Eooms in 160 Acres.49 

9. Area of Booms and Tons of Coal per Room.50 

10. Area of Room Cross-Cuts (per Cross-Cut), Tons of Coal Produced and 

Yardage Cost.50 

11. Total Cross-Cut Yardage Cost per Room.51 

12. Tons of Coal in Cross-Cuts per Room.52 

13. Cost of Props for Room and Cross-Cuts at One-Half Cent Per Square 

Foot, 180-Foot Rooms.52 

14. Cost of Props for Room and Cross-Cuts at One-Half Cent per Square 

Foot, 210-Foot Rooms.53 


o 

















PANEL SYSTEM OF COAL MINING 
A GRAPHICAL STUDY OF PERCENTAGE OF EXTRACTION 


I. Introduction 

1. Reasons for the Investigation. —In 1917 an investigation* 
of the percentages of coal extracted and lost in Illinois and in other 
bituminous coal mining districts showed that the percentage obtained 
is less than is commonly believed. The conclusions reached in the 
earlier investigation naturally led to the study of the panel system to 
determine the greatest possible extraction with different dimensions of 
workings. 

2. Other Investigations .—Investigations of a similar nature have 
been made to determine the relation between dimensions of workings 
and amounts of extraction. Special mention should be made of the 
work of J. C. Quade, G. E. Lyman, and J. C. Gibson, whose methods 
are described on pages 46, 66, and 70. So far as is known, 
however, no study of the panel system in general with regard to the 
percentage of extraction and the change of this percentage with 
change of dimensions of workings has hitherto been made. 

3. Acknowledgments .—The work of the Illinois Coal Mining In¬ 
vestigations is carried on under the direction of Professor H. H. Stoek, 
head of the Department of Mining Engineering, University of Illi¬ 
nois; F. W. De Wolf, Chief, State Geological Survey Division; and 
G. S. Rice, Chief Mining Engineer, U. S. Bureau of Mines. Professor 
Stoek has been especially helpful in carefully revising the manuscript. 

4. Summary. —The investigation shows that the highest extrac¬ 
tion which can possibly be attained under the conditions assumed, 
with rooms 300 feet long and 30 feet wide on 50-foot centers, is only 
57.05 per cent. Even if the improbable ratio of room to pillar width 

*Young, C. M., “Percentage of Extraction of Bituminous Coal with Special Reference 
to niinois Conditions.” Illinois Coal Mining Investigations, Univ. of Ill. Eng. Exp. Sta., 
Bui. 100, 1917. 


7 




8 


ILLINOIS ENGINEERING EXPERIMENT STATION 


of 4 to 1 (40-foot rooms on 50-foot centers) is assumed, the highest 
attainable extraction is 68.48 per cent. No better results than these 
can be reached unless the amount of coal left in room pillars or in 
barrier pillars is reduced. As a matter of fact, the average extraction 
throughout the State is not more than 50 per cent and in those parts 
where coal is thickest and lies at greatest depth, the extraction will 
not average so much. The lowest extractions are due in part to the 
leaving of top coal; thus the actual extraction in some districts is 
lower than that indieated by calculation on an area basis. 

The percentage of extraction increases with the increase of ratio 
between room width and pillar width, with length of rooms and with 
number of rooms per entry, but the diagrams showing the effect of 
changes of dimensions on percentages of extraction indicate that, 
except in the case of ratio of room width to pillar width, very nearly 
the maximum effect of these changes has been reached by the dimen¬ 
sions considered, i. e., room length from 200 to 300 feet, room width 
from 20 to 40 feet, number of rooms per entry from 8 to 24. Further 
increase of length of rooms or of number of rooms per entry would 
not materially increase the percentage of extraction. 

The percentage of extraction could be further increased by in¬ 
crease of room width in relation to pillar width, but it is only rarely 
that a ratio of even 4 to 1 can be used.without the production of 
squeezes. The conclusion is, therefore, warranted that the extraetion 
under a panel system of mining, which relies upon coal left in the 
ground for the support of the overburden, cannot be greater than 
about 68 per cent unless a smaller amount of coal is left in the form 
of barrier pillars than is assumed in this investigation. 

5. Reasons for Low Extraction .—There are two essential reasons 
for low extraction. The first is the leaving of top coal, because the 
roof needs support or because the bed is too thick for convenient min¬ 
ing of the whole thickness. Such losses occur principally in the thick 
coal of the southern part of the State. When some support for the 
roof is necessary and when it can be furnished by coal left in place at 
less cost than by artificial means, the leaving of coal is justified, 
commercially, though such loss may still be criticized from the stand¬ 
point of conservation. In some places, however, the thickness of coal 
left is much greater than is necessary to support the roof, and it is 
probable that a considerably larger amount of the coal might be ex¬ 
tracted at a cost which would allow a profit on the top coal mined. 


PANEL SYSTEM OF COAL MINING 


9 


The second reason for low extraction lies in the method of 
mining which depends upon coal, left in the form of pillars, to sup¬ 
port overlying material. The use of coal for such support may be 
considered: first, for the support of the immediate top until a place 
has been worked out, and secondly, for the permanent support of the 
overburden to prevent subsidence of the surface. 

In the first case large pillars would commonly be unnecessary 
and the ratio of room width to pillar width might be large. Under 
this case may be considered such operations as those in Fulton County, 
discussed in Appendix I, where no attempt is made at permanent sup¬ 
port of the surface, and where coal left in pillars may be considered 
as serving the same purpose as props. Pillars which are 8 feet wide 
near the entry are tapered to almost nothing at the end; yet these 
pillars serve their purpose of support to the immediate top until the 
coal has been worked out. Under such circumstances it is possible 
to extract from 70 to 80 per cent of the coal, but such results would 
be unattainable in thick coal because the strength of a pillar decreases 
rapidly as its height increases, and consequently greater pillar width 
would be necessary to furnish the support needed. 

The second case is that of the use of coal in the form of pillars 
as a permanent support for the overburden, and this use constitutes 
the principal reason for low extraction. A much higher percentage 
of coal might be obtained if the surface were allowed to subside. 
Under present conditions, however, this practice is not often con¬ 
sidered practical, especially where ownership of the coal and the 
surface is separate, because the operator is often compelled to pay 
very high damages for any disturbance of the surface. 

While no general rule can be stated for the determination of 
the dimensions of pillars and of the ratio of pillar area to room area 
necessary for the permanent support of the surface at a given depth, 
it is known that the relative area of pillars must be made greater 
as the depth increases. Experience in Illinois shows that the surface 
cannot be permanently sustained over the deeper and thicker beds 
of the State unless about half of the coal is left. This statement is 
true in general for Districts V, VI, and VII, of the Illinois Coal 
Mining Investigations, which include bed 5 in Saline and Gallatin 
counties and nearly all mines in the No. 6 coal. 

No high percentage of extraction is possible without subsidence 
of the surface unless the space left by the coal is filled, probably by 
washing fine material into the mine through pipes. Illinois mines are 


10 


ILLINOIS ENGINEERING EXPERIMENT STATION 


in general nearly level and it would be difficult to transport the filling 
material along the entries by means of water; also the removal of the 
water would be difficult and expensive. For these reasons the method 
appears at present to he impractical in Illinois; therefore if high 
extraction is to be obtained subsidence must be expected and con¬ 
trolled as is being successfully done in some districts where extraction 
of more than 90 per cent is customary. 


PANEL SYSTEM OF COAL MINING 


11 


II. Advantages of Greater Extraction 

The principal advantages of higher extraction may be sum¬ 
marized as follows: 

6. Investment per Ton of Total Output .—If the amount of coal 
extracted could be increased from 50 to 100 per cent, the investment, 
per ton of total coal produced for surface plants, shafts, entries, etc., 
would be reduced by half because twice as much coal would be handled 
with the equipment. Maintenance charges, however, would not be 
similarly reduced since the colliery would be in operation for twice 
as long if the same territory were involved. The cost per ton of 
coal in the ground would be decreased by one-half when the coal is 
purchased in fee, and where it is leased on royalty the owner of the 
land would receive twice as much as he formerly received. 

7. Cost of Haulage .—The cost per ton for moving the coal from 
the working place to the shaft would be decreased, because the 
average length of haul would be only half as much as with 50 per 
cent extraction. Twice as much coal would be hauled through the 
entries, so that the cost per ton of coal for maintaining entries would 
be lessened. Since the element of time is also involved, it is not possible 
to say that the cost for maintenance would be reduced by 50 per cent. 

8. Cost of Ventilation .—The average distance from the shaft of 
places to be ventilated being only half as much as with 50 per cent ex¬ 
traction, the expense of ventilation would be decreased. Ventilation 
would be simplified, because worked-out places would cave and would 
require no attention except the provision of bleeders or of seals. 

To summarize, the cost per ton of total coal for all installations 
and excavations which would not need renewal because of the increased 
time of service would be reduced by 50 per cent. In operations whose 
costs are affected by the distance from the shafts to the point of pro¬ 
duction, the costs would be reduced in proportion to the effect of the 
distance. While it cannot be expected that an extraction of 100 per 
cent will be obtained, an extraction of 90 per cent should not be 


12 


ILLINOIS ENGINEERING EXPERIMENT STATION 


difficult from an engineering standpoint, and the economies resulting 
would be in proportion to the increase. 

9. Efficiency of Supervision .—Appreciation of the need of thor¬ 
ough supervision to preserve mines in working condition and to pre¬ 
vent accidents is increasing, but under present mining practice the 
visits to a working place can be made more frequent only by increas¬ 
ing the supervising force, thus adding to the cost of coal. With greater 
extraction the concentration of workings would eliminate a part of 
the time now lost in travel, and thus would help to solve the problem 
of increased supervision. 

10. Prevention of Waste .—The greatest ultimate advantage of 
higher extraction would be the increase of the available reserves of 
coal. At present this advantage is largely overlooked, because the 
reserves of coal of the quality and thickness now mined are sufficient 
for many years. Unfortunately, however, it is the best coal and that 
easiest to produce which is being lost, and the coal which will be 
available when the reserves are exhausted will certainly be more 
costly and perhaps not so good. Even if the question of reserves is 
neglected because no immediate exhaustion is possible, it is a subject 
for great regret that a substance as valuable as coal should be un¬ 
necessarily lost. 

There is no doubt of the ability of mining engineers to plan 
operations to get high extraction. The methods are well known and 
are employed with great advantage and without great difficulty in 
some districts, and there is no reason to doubt their success in Illinois. 
The problem is more one of immediate commercial advantage than one 
of engineering practice. 


PANEL SYSTEM OF COAL MINING 


13 


III. Principles Involved in High Extraction 

High extraction requires the mining of pillar coal. Three prin¬ 
ciples are involved in the successful extraction of this coal: first, 
the strain on the roof above the rooms must not be great enough 
to cause the roof to fall before the pillar coal is removed; secondly, 
the strain on the pillars must not be great enough to cause squeezing; 
thirdly, additional strain on the pillars, due to pillar drawing, must 
be prevented by the breaking of the roof behind the retreating pillar 
face. 

The fall of the roof can be prevented by making the room suffi¬ 
ciently narrow, or at least the strain can be decreased so that proper 
timbering will prevent falls. This does not necessarily involve low 
ratio of room width to pillar width. If the pillars are to be removed, 
however, they will necessarily be made large enough for convenient 
working. In some districts where pillar coal is successfully mined 
and where high extraction is reached, rooms are made very narrow 
and are, in fact, little more than openings for ventilation and for 
access to the pillar coal. Such extreme narrowness is necessary only 
under bad top, and rooms in most places in Illinois could probably 
be made 20 feet wide without interference with successful pillar work. 

The strain on the pillars due to the weight of the overburden 
must be kept within the limits of strength of the pillars themselves 
and of the top and bottom. When the room coal is removed, the 
weight of the overlying material is transferred to the pillars and 
these must be made large enough to stand the strain without being 
crushed or pressed into the top or bottom. 

When the extraction of the pillar coal is commenced at the end 
of the room, a part of the weight of the overburden above the portion 
removed is transferred to the remaining pillars, thus increasing the 
strain. This strain may be relieved by the breaking of the roof be¬ 
hind the retreating pillar face. 

If enough coal is left in pillars to prevent crushing before pil¬ 
lar drawing begins, and if the strain is relieved by the breaking of 
the roof during pillar drawing, squeezes will be entirely prevented. 

These three principles: rooms narrow enough for the support 
of the roof, pillars large enough to stand without crushing, and 


14 


ILLINOIS ENGINEERING EXPERIMENT STATION 


relief of additional strain due to pillar drawing by the breaking 
of the roof, are successfully applied in some mining districts in this 
country. There is nothing in the physical conditions of the Illinois 
coal fields to indicate that the application of these principles is im¬ 
possible or even unusually difficult. 


PANEL SYSTEM OF COAL MINING 


15 


IV. Method op Investigating the Percentages of Extraction 

The object of the calculations hereinafter described was the deter¬ 
mination of percentages of extraction when plans for the develop¬ 
ment of a mine are carefully made and all dimensions accurately 
followed. It was necessary to consider a hypothetical mine or a part 
of one consistently developed on some predetermined plan. The 
discussion has been confined to the panel system, because it repre¬ 
sents the highest development reached in the extraction of coal by 
rooms and pillars. It is upon this system that all large modern mines 
in Illinois are projected. 

The term panel system originally implied the isolation of a group 
of rooms, called a panel, from other such groups or panels, by a 
surrounding pillar of coal pierced on one side only by the room en¬ 
tries. The term is now frequently applied to a system in which the 
room entries do not terminate in the panel but are driven through 
to the next cross entry, the block of rooms thus being opened at both 
ends instead of only at one, the pillars between the ends of panels 
being omitted. 

The present tendency in Illinois seems to be toward the adoption 
of a more nearly completely isolated panel than has been used 
though the fire pillars remaining are too narrow to resist squeezing. 
On this basis the values in the tables and diagrams given have been 
calculated. The assumed pillars between the ends of adjacent panels 
are, however, very thin and approximately the same values will be 
found if these pillars are omitted. The figures and diagrams will 
apply very closely to either form of the panel system. 

11. Basis of Calculation .—In the following discussion extraction 
is calculated on the basis of area excavated instead of on that of 
tonnage produced. When the workings are of uniform height through¬ 
out the mine, the extraction on the basis of tonnage is proportional 
to that on the basis of area, but, if a portion of the coal is left at 
top or bottom as is frequently the case in thick coal and under a poor 
roof, the ratio of tonnage to area may vary in different parts of the 
mine. Whenever coal is left on the top or bottom, the extraction on a 
tonnage basis is less than that on an area basis. To get the per- 


16 


ILLINOIS ENGINEERING EXPERIMENT STATION 


centage of extraction on a tonnage basis from that on an area basis, 
the latter should be multiplied by the ratio of thickness mined to the 
total thickness of the bed. In some parts of Illinois, for example, 
where the thickness of the coal is nine feet or more, only about seven 
feet of the coal is extracted. In such places the tonnage produced 
cannot be more than seven-ninths, or 78 per cent, of that indicated 
by the area excavated and is less if the thickness of the coal is greater 
than nine feet. This fact should be borne in mind in considering the 
percentages of extraction given in this bulletin. In other words 
these percentages are the maximum amounts of coal which it is possible 
to get with the given dimensions of workings without the gouging of 
pillars or the extraction of pillar coal on the retreat. As there is 
always some waste in mining, the extractions obtained in practice 
with similar dimensions may be expected to fall below those indi¬ 
cated in the tables. The amount of waste is variable, but it is doubt¬ 
ful if it is ever less than 5 per cent. 

12. Method of Computation .—An area of 160 acres was selected 
as large enough to give sufficiently accurate results, and workings 
were laid out for this area. Since an area of nearly an acre is worked 
out per day in the larger mines, which produce 4000 tons, or more, per 
day as now operated in Illinois, it will be seen that 160 acres is 
only a small part of the tract developed by a single large mine; in 
fact it represents only about 160 days’ work. Accordingly in plan¬ 
ning the projection, no attempt was made to lay out 160 acres as a 
complete mine, but this small tract was assumed to be part of a larger 
district and was treated as if a square of 160 acres had been taken 
from the map of a large mine. 

If the 160 acres had been developed by itself, one would natural¬ 
ly assume that the main entry was driven through the middle of the 
tract and that the cross entries were driven equal distances to each 
side. Instead of this assumption it was determined as a matter of sim¬ 
plification that the line of the ends of a series of panels driven from 
one cross entry should constitute one border, m - n, and the sides of 
a series of panels should constitute another border, n - o (Fig. 1). 

In this 160-acre tract workings were laid out with different 
dimensions and the percentages of extraction for these different dimen- 
sions calculated. The room lengths chosen were 200 feet, 250 feet, 
and 300 feet. The numbers of rooms per entry chosen were 8, 12, 16, 


PANEL SYSTEM OF COAL MINING 


17 



Fig. 1. Map of 160-Acre Tract Selected for Investigation 


20, 24, and 28. The cases assumed include, of course, only a few of 
the many dimensions and numbers of rooms that may occur, but they 
show the effects of variation in dimensions and number. 

For the first calculation it was assumed that all rooms should 
be 25 feet wide and driven on 50-foot centers. After the method 
had been developed for these dimensions, calculations were made for 
different room widths, namely, 20, 30, 35, and 40 feet. Other assump¬ 
tions made with regard to various portions of the workings will be 
explained in the detailed consideration of the calculations of area 
and extraction. 

No allowance was made for a barrier pillar around the tract 


Cross Entries 



































































18 


ILLINOIS ENGINEERING EXPERIMENT STATION 


since the barrier pillar left around the borders of a mine constitutes 
only a very small percentage of the total area, and the proportion 
which would be chargeable to an area of 160 acres would be insignifi¬ 
cant. 

One result of the limitation of the area is the occurrence of' 
certain irregularities in the percentages of area occupied by different 
portions of the workings and in the percentages of extraction. These 
irregularities would not be found if a larger tract were under con¬ 
sideration. They will be explained in the discussion of the diagrams 
showing areas and percentages of extraction (Figs. 4 to 9). 


The dimensions assumed are as follows: 


Eutry width . 

Main entry pillar . 

Cross entry pillar . 

Eoom entry pillar . 

Entry cross-cut width . 

Entry cross-cut centers . 

Barrier pillars . 

Pillars at sides of panels . 

Pillars at ends of panels . 

Eoom neck, width . 

Eoom neck, length . 

Distance from entry rib to point where room reaches 

full width . 

Eoom cross-cut width . 


Feet 

12 

25 

25 

20 

12 

72 

100 

20 

25 

18 

12 

18 

18 


The constant quantities in the calculations are the dimensions of 
the tract under consideration, the widths of entries and entry pillars, 
the spacing and width of entry cross-cuts and room cross-cuts, the 
dimensions of room necks, and the widths of barrier pillars and of 
pillars at sides and ends of panels. The variables are the length 
of rooms, the width of rooms, and the number of rooms per panel. 
Changes in these variables involve changes in the percentages of 
area occupied by different portions of the workings and in the per¬ 
centage of extraction in the portions occupied by rooms and pillars. 


13. Method of Procedure .—The method of procedure involved; 
first, the determination of the percentage of coal won or lost in any 
portion of the workings, such as rooms and pillars, and barriers, and 
secondl}', the determination of the percentage of the entire area 















PANEL SYSTEM OP COAL MINING 


19 


occupied by this portion. A calculation was made, for example, of 
the percentage of extraction inside a panel and then of the per¬ 
centage of the total area occupied by panels. A summation of the 
extractions in different workings gave the total extraction. 

Three classes of workings are considered: (1) rooms and pillars, 
(2) entries, and (3) pillars outside the panels. These divisions are 
taken up separately and in order. 

In determining the area exca^mted in the room and pillar area 
of the panel, that is, the area of the panel mined out with the excep¬ 
tion of the room entry, cdef and ghik, Fig. 1, a calculation of the 
area of a single room and its cross-cuts was made. This area was 
multiplied by the^ number of rooms per panel, proper allowance 
being made for the fact that there is always one more room than 
pillars on an entry and that the total area of cross-cuts is calculated 
from the number of pillars. To calculate the area taken out per room 
the area lost at the neck was subtracted from the product of the 
width and the length of the room. 

The forms and the dimensions of the room necks and cross-cuts 
are shown in Fig. 2. The area lost at the room neck in the case of a 
room 25 feet wide is 

1 Q I 1 O 

2 X 3.5 X -= 105 square feet 

In all cases it was assumed that cross-cuts were staggered and 
that the number of cross-cuts through any pillar was either one more 
or one less than that made through the adjoining pillars. Cross-cuts 
were so spaced that no working place would be driven more than 
60 feet ahead of the air current. This arrangement gives an average 
of cross-cuts per pillar for the 200-foot rooms, and 2^ for the 
250-foot rooms. This method of arranging cross-cuts is common but 
not universal. The percentage of area occupied by cross-cuts is 
small, however, and it makes little difference, so far as the per¬ 
centage of extraction is concerned, whether the cross-cuts are as¬ 
sumed to be in a straight line or staggered. The area of cross-cuts 
per pillar in the case of the 250-foot room is 

2.5X18X25 = 1,125 square feet 

Tlie area of the rooms turned from one entry, with their cross¬ 
cuts, assuming 12 rooms per entry and a room length of 250 feet, is 

12 [(25X250)-105] -f (11 X2.5X18X25) =86,115 square feet 



-* 1 *— so —^ /S'* 


ILLINOIS ENGINEERING EXPERIMENT STATION 



Fig. 2. Eoom Entry and Room Necks 
















PANEL SYSTEM OP COAL MINING 


21 


In the following computations it is assumed that rooms are 
turned from both the room entries, and the area of the number of 
rooms and room cross-cuts in the panel is 

2X86,115 = 172,230 square feet 

The area devoted to rooms and pillars in a panel of 12 rooms, 
25 feet wide on 50-foot centers and 250 feet long, is 

[24X25X250] -[- [22X25X250] =287,500 square feet 
and the percentage of extraction is 


172,230X100 

287,500 


= 59.91 per cent 


14. Lengths of Entries .—The lengths of entries are obtained 
by measurement or by calculation. The length given in each case 
is that of the double entry, e. g., the length of the main entry is 
2640 feet. 

15. Percentage of Extraction in Entries .—^With the following 
notation, 


Le = length of entry 
ire = width of entry 

?i = number of entries (2 for double entry, 3 for triple entry) 
Wp = width of entry pillar 
Tbc = width of cross-cuts 
Cc = cross-cut centers 

the percentage of extraction in any entry or group of entries is ex¬ 
pressed by the formula: 

[{nXLe'KWe) -f (n —1) (-^XTTcXlbp)] X 100 
{n'KLey.We) + (n —1) Xl/eXlTp 

With the dimensions assumed on page 18, the percentage of 
extraction in room entries is 

((2X12)+ (i|x20)lX 100 


44 


= 62.12 per cent 






22 


ILLINOIS ENGINEERING EXPERIMENT STATION 


In the same way the percentage of extraction in main entry and 
cross entries is 


[(2X12) 4-X25)] XlOO 
-:—-= 57.48 per cent 

The difference in extraction between the main and cross entrie.s 
and the room entries is due to the differences in width of entry pillars. 

The area extracted in the room entries inside the panel is equal 
to the area occupied by the entries and entry pillar multiplied by 
the percentage of extraction: 

44X575XO.6212 = 15,716>quare feet 


16. Percentage, of Extraction Inside the Panel. — The total 
area extracted inside the panel is the sum of the areas of rooms with 
their cross-cuts and of the entries and their cross-cuts, 

172,230 + 15,716 = 187,946 square feet 


and the percentage of extraction is 


187,946X100 

544X575 


= 60.09 per cent 


in which 544 is the width of the panel and 575 the length. 


17. Percentage of the Total Area Occupied by Panels. —In any 
restricted area, such as that under consideration, there will be in most 
instances a number of whole panels and parts of others which can be 
determined by plotting or by computation. In the case under con¬ 
sideration, which is illustrated in Fig. 1, there were 12 whole panels 
544 by 575 feet, 3 parts of panels 155 by 575 feet, 1 part 155 by 
392 feet, and 4 parts 544 by 392 feet. The total area of the panels 
was then: 


Square Feet 

12X544X575=3,753,600 
3X155X575= 267,375 
155X392= 60,760 

4X544X392= 852,992 


4,934,727 





PANEL SYSTEM OF COAL MINING 


23 


The total percentage of area occupied by panels is 


4,934,727X100 

6,969,600 


= 70.80 per cent 


18. Percentage of Total Area Extracted in All Panels. —This 
is the product of the percentage of total area occupied by panels 
and the percentage of extraction in panels: 


70.80X0.6009 = 42.54 per cent 


19. Entry Area Outside the Panels. —A double main entry is 
assumed to be driven across the tract, its area being 2,640 X 49 == 
129,360 square feet. In the case of the two double cross entries 
the width is the same, but the length is less by the width of the main 
entry from which the two cross entries are driven. The area of 
these two is 


2X2,591X49 = 253,918 square feet 

The area devoted to the main entry was the same in all instances 
since only one main entry was assumed. The area of cross entries 
varied considerably as there were sometimes three cross entries, some¬ 
times two and sometimes only one. 

The area of room entries outside the panel is 

■ 16X44X100 = 70,400 square feet 

In the tract under consideration, illustrated in Fig. 1, there are 
no fractional widths of cross entry barriers to be considered and 
all the portions of room entries outside the panels are 100 feet long. 
In some other cases there were fractions of barrier pillars and there¬ 
fore different lengths of room entries outside the panels. 

, , The total area occupied by entries outside the panels is the 

sum of the areas of main entry, cross entries, and room entries with 
their entry pillars: 

Square Feet 

Main entry. 129,360 

Cross entries. 253,918 

Room entries . 70,400 


< 

■1 i-A 


453,678 







24 


ILLINOIS ENGINEERING EXPERIMENT STATION 


The area of the room entries and entry pillars inside the panels is 
12X44X575 + 4X44X392 = 372,592 square feet 


20. Percentage of Area Occupied by Entries. —The percentages 
of total area occupied by entries are as follows: 


Main entry 


129,360X100 

6,969,600 


= 1.86 per cent 


Cross entries 


253,918X100 

6,969,600 


= 3.64 per cent 


Room entries—outside panels 


70,400X100 

6,969,600 


= 1.01 per cent 


Room entries—inside panels . 


372,592X100 

6,969,600 


= 5.35 per cent 


The percentage of the total area occupied by room entries both out¬ 
side and inside the panel is 

1.01 + 5.35 = 6.36 per cent 

21. Percentage of Total Area Extracted in Entries. —To get the 
percentage of total area extracted in entries, the percentage of area 
occupied by the entry is multiplied by the calculated percentage 
of extraction, as follows: 

Percentage 

Percentage of total^area extracted in room entries 

inside panels.5.35 XO. 6212 = 3.32 

Percentage of total area extracted in room entries 

outside panels.1.01X0.6212 = 0.63 

Percentage of total area extracted in cross entries . 3.64 X0.5748 = 2.09 
Percentage of total area extracted in main entry . 1.86 XO.5748 = 1.07 


Total percentage extracted in entries 


7.11 


22. Summary of Percentages of Extraction. —The extraction in 
the different parts of the mine may then be summarized as follows: 

Percentage 

Panels.42.54 

Room entries—outside panels.0.63 

Cross entries.2.09 

Main entry.1.07 


Total . 


46.33 















PANEL SYSTEM OF COAL MINING 


25 


23. Area Left in Pillars Outside the Panels .—The only area 
remaining to be considered is that occupied by barrier pillars and 
pillars at sides and ends of panels. As it is assumed that this pillar 
coal is entirely lost the only thing to be considered is the area and 
the percentage of total area occupied by the pillars. If in any case 
it is to be assumed that some of this coal is to be saved, the amount 
thus extracted may be found by multiplying the area of the pillars 
by the percentage of extraction. 

It is, of course, not always true that all the coal thus left is 
lost, and theoretically this is seldom the case, as it is generally in¬ 
tended that a large part of the coal left, especially in barrier pillars, 
will be extracted later. In some coal mining districts this coal is 
extracted, but in the Illinois fields very little of the barrier coal is 
mined; consequently it seems better to assume complete loss of this 
coal rather than an arbitrary percentage of recovery. 

In the case of each entry barrier the area is the length of the 
barrier multiplied by its width, minus the area of the entries which 
extend through it but including the entry pillar. The area of the main 
entry barrier pillars, as thus defined, is 

2X100X2640 - [(8X100X12) + (4X25X12)] = 517,200 square feet 

The percentage of the total area devoted to main entry barrier 
pillars is 


517,200X100 

6,969,600 


= 7.42 per cent 


This percentage is unusually high because of the small area con¬ 
sidered. In the case of a square area of 5,000 acres with one main 
entry with barrier pillars 100 feet wide, the percentage of area 
occupied by the main entry barriers is about 1.3 per cent. 

The length of the cross entry barrier pillars is the distance 
across the tract minus the width of the main entry with its two 
barrier pillars. The area is 


4X100(2640—249) — [(32X100X12)]+X16X20X12)] = 914,160 square feet 


The percentage of total area is 


914,160X100 

6,969,600 


= 13.12 per cent 




26 


ILLINOIS ENGINEERING EXPERIMENT STATION 


■ The area left in pillars at the ends of panels is, in the cases 
assumed 

; 25X (2640—249) = 59,775 square feet 

The percentage of the total area occupied by these pillars is 


59,775X100 

6,969,600 


= 0.86 per cent 


The area of the pillars left at the sides of panels is, in the case 
assumed 


(9X20X575) + (3X20X392) = 127,020 square feet 
The percentage of total area occupied is 


127,020X100 

6,969,600 


= 1.82 per cent 


The sum of the various items of loss in pillars outside the panels 
and entries is 


Main entry barrier.7.42 

Cross entry barrier.13,12 

Total in entry barriers .20.54 

In pillars at ends of panels.0.86 

In pillars at sides of panels.1.82 


Total left in pillars outside the panels.23.22 

24. Percentages of Extraction ivith Different Room Widths .— 
In computing the percentage of total extraction with various other 
room widths considered: viz.,- 20, 30, 35, and 40 feet the dimensions 
of room centers were kept unchanged at 50 feet. It is recognized 
that this would not be the practice, but a change of room centers 
would have so complicated the problem as to require a much longer 
period for the attainment of results. The method of calculation 
has been clearly indicated and it is possible, by selecting room and 
pillar widths of the proper ratio in Tables 4, 5, and 6 to obtain close 
approximations to the percentages of extraction and loss with any 
widths of room and pillar desired. 

It was assumed that the length of the panels and the percentage 
of total area devoted to panels for each number of rooms per entry 











PANEL SYSTEM OF COAL MINING '27 

were not changed by these alterations in room and pillar dimensions. 
This assumption is not strictly true, since the length of the panel 
varies with the room width; for example, a panel of eight 40-foot 
rooms to the entry is 390 feet long instead of the 375 feet assumed. 
The discrepancies are greatest in the instances of widest rooms, because 
the difference between real panel length and assumed panel length Is 
greatest. There are two errors which partially neutralize each other, 
and it was found by computation for the extreme cases that the final 
errors were very small. In the first place if the panel is actually 
longer than is assumed, the percentage of extraction in the panel is 
less than that computed. In the second place if the panel is longer 
than assumed, the total area occupied by panels is greater than 
that computed. The errors for the first and the last figures in the 
various columns of Table 4 are as follows: In the column for 
20-foot rooms the first figure is 0.05 too high and the last figure is 
0.29 too low; in the column for 25-foot rooms the figures are correct; 
in the column for 30-foot rooms the first figure is 0.05 too low and 
the last figure 0.04 too high; in the column for 35-foot rooms the 
first figure is 0.11 too low and the last figure 0.25 too high; in the 
column for 40-foot rooms the first figure is 0.15 too low and the last 
figure 0.67 too high. The other figures in each column have errors 
intermediate between those of the first and last figures. The errors 
all being less than one per cent, it is apparent that this method of 
calculation is sufficiently accurate for all purposes for which it is 
likely to be used, as departures from the projected method of work¬ 
ing will account for greater differences between the actual and the 
computed output than the small errors in the tables. 


25. Tables and Diagrams .—For convenience in reference the 
values obtained by the methods described in the preceding pages 
have been collected in Tables 1-7, which give the percentages of total 
area occupied by different classes of workings, the percentages of 
extraction in these different classes, the percentages of total area 
excavated in the different classes of workings, the percentage of total 
area won, the lengths of entries and the amounts of narrow work. 

Most of the facts given in the tables are shown graphically in 
Figs. 3 to 9. These figures permit comparison between the results 
obtained by the use of different dimensions of workings. 

For 25-foot rooms. Table 1 shows in column 3 the percentage of 


^xitracr/on /n3/We /^c7/7&/-f<9rCiff/7/‘ 


28 


ILLINOIS ENGINEERING EXPERIMENT STATION 


Table 1 

Extraction in Panels 


25-Foot Rooms 


Length of 
Rooms 
(Feet) 

Number of 
Rooms per 
Room Entry 

Percentage of 
Extraction in 
Room and 
Pillar Areal 

Percentage of 
Extraction 
inside the 
Panel 

Percentage cf 
Total Area 
Occupied by 
Panels 

Percentage of 
Total Area 
Extracted 
in Panels 


8 

58.51 

58 

.87 

62.17 

36.60 


12 

57.54 

57 

.99 

70.20 

40.71 

200 

16 

57.06 

57 

.56 

77.09 

44.37 


20 

56.78 

57 

.31 

78.45 

44.96 


24 

56.60 

57 

15 

78.45 

44.83 


28 

56.47 

57 

03 

79.28 

45.21 


8 

60.89 

60 

92 

62.71 

38.20 


12 

59.91 

60 

09 

70.80 

42.54 

250 

16 

59.45 ' 

59 

67 

77.76 

46.40 


20 

59.19 

59 

43 

79.14 

47.03 


24 

59.01 

59. 

27 

79.13 

46.90 


28 

58.89 

59. 

15 

79.97 

47.30 


8 

62.39 

62 

37 

63.25 

39.45 


12 

61.49 

61 

53 

71.41 

43.94 

300 

16 

61.05 

61. 

12 

78.43 

47.94 


20 

60.80 

60 

88 

79.81 

48.59 


24 

60.63 

60 

73 

79.81 

48.47 


28 

60.51 

60 

62 

80.65 

48.89 


IRoom aud pillar area shown by hatching in Fig. 1. 



Number of /^oom5 per ^nfr^ 


Fig. 3. Percentage of Extraction Inside the Panel for Rooms 
250 Feet Long, 25 Feet Wide, on 50-Foot Centers 






















































PANEL SYSTEM OP COAL MINING 


29 


extraction in the room and pillar area obtained with each length 
of room and each number of rooms per entry; in column 4 the total 
percentage of extraction inside the panel, that is, the sum of the 
extraction in rooms and room cross-cuts, and in room entries; in col¬ 
umn 5 the percentage of the total area included in panels; and in 
column 6 the percentage of the total area extracted in panels. The 
percentage extracted in the panels plus the percentage extracted in 
the entries outside the panels gives the total percentage of extraction. 

The values in column 4 of Table 1, the percentage of extraction 
inside the panel for rooms 25 feet wide, are illustrated by Fig. 3. 
For a given width of room and pillar the percentage of extraction 
inside the panel decreases somewhat as the number of rooms per entry 
increases, because the proportion of the total panel area remaining 
in pillars increases as the number of rooms increases and the per¬ 
centage of extraction correspondingly decreases. With only two rooms 
and one pillar approximately 1/3 of the coal is left in the pillar, 
while with the 10 rooms and 9 pillars Ho remain and with 20 rooms 
and 19 pillars remain. 

The values in column 5 of Table 1 are illustrated in Fig. 4 which 
shows the percentage of total area included in panels for 25-foot 
rooms, 200 feet, 250 feet, and 300 feet long respectively, and for 8, 12, 
16, 20, 24, and 28 rooms per entry. These diagrams show that the per¬ 
centage of area devoted to panels increases with the length of the room 
and the number of rooms per entry. The increase is especially rapid 
for the smaller number of rooms per entry and comparatively small 
for the larger number of rooms per entry. 

It will be noticed that there is a reversal in the direction of the 
lines at 24 rooms per entry shown in the broken lines based on the 
figures in the table, and that there is no corresponding change in 
direction of the diagrams for percentage of extraction inside the panel. 
These facts show that the drop in the diagrams of total extraction 
(Fig. 6) at 24 rooms per entry is due to the irregularity of the increase 
of percentage of total area included in panels, which in turn is due to 
the limited area considered. The solid lines (Figs. 4 and 6) show the 
positions when a large area is considered, and the same results are 
reached by calculation for 25 rooms per entry. 

It will also be noticed that there is a comparatively rapid change 
in the direction of the lines when there are about 16 rooms per panel. 
This fact indicates that with 16 rooms per panel, or less, the percent- 


/^or/'/on of Toro/ /4reo /n f^one/o /n f^or Cent 


30 


ILLINOIS ENGINEERING EXPERIMENT STATION 



f/um/rer of Too mo perTn/ry 


Fig. 4. Percentage of Total Area Included in Panels for Eooms 

25 Feet Wide, on 50-Foot Centers 

« 

age of area occupied by panels increases rapidly with the number of 
rooms per entry. For 16 rooms, or more, the increase is slow. This 
change also shows as does the diagram for total percentage of extrac¬ 
tion, that this percentage increases comparatively rapidly with the 


























































PANEL SYSTEM OP COAL MINING 


31 


increase of number of rooms per entry to about 16 and that after this 
number is reached the rate of increase is small. 


Table 2 

Extraction in Entries 


Length 

of 

Rooms 

(Feet) 

Number 

of 

Rooms 

per 

Room 

Entry 

Percentage of Total Area Occupied 
by Entries 

Percentage of Total Area 
Extracted in Entries 

Main 

Entry 

Cross 

Entry 

Room Entry 

Total 

Main 

Entry 

Cross 

Entry 

Room 

Entry 

Total 

Outside 

Panel 

Inside 

Panel 


8 

1.86 

5.46 

1.79 

5.92 

15.03 

1.07 

3.14 

4.79 

9.00 


12 

1.86 

3.64 

1.26 

6.68 

13.44 

1.07 

2.09 

4.93 

8.09 

200 

16 

1.86 

1.82 

0.76 

7.34 

11.78 

1.07 

1.05 

5.03 

7.15 


20 

1.86 

1.82 

0.63 

7.47 

11.78 

1.07 

1.05 

5.03 

7.15 


24 

1.86 

1.82 

0.63 

7.47 

11.78 

1.07 

1.05 

5.03 

7.15 


28 

1.86 

1.82 

0.63 

7.55 

11.86 

1.07 

1.05 

5.08 

7.20 


8 

1.86 

5.46 

1.43 

4.74 

13.49 

1.07 

3.14 

3.83 

8.04 


12 

1.86 

3.64 

1.01 

5.35 

11.86 

1.07 

2.09 

3.95 

7.11 

250 

16 

1.86 

1.82 

0.61 

5.87 

10.16 

1.07 

1.05 

4.02 

6.14 


20 

1.86 

1.82 

0.51 

5.97 

10.16 

1.07 

1.05 

4.03 

6.15 


24 

1.86 

1.82 

0.51 

5.97 

10.16 

1.07 

1.05 

4.03 

6.15 


28 

1.86 

1.82 

0.51 

6.04 

10.23 

1.07 

1.05 

4.07 

6.19 


8 

1.86 

5.46 

1.43 

4.74 

13.49 

1.07 

3.14 

3.83 

8.04 


12 

1.86 

3.64 

1.01 

5.35 

11.86 

1.07 

2.09 

3.95 

7.11 

300 

16 

1.86 

1.82 

0.61 

5.87 

10.16 

1.07 

1.05 

4.02 

6.14 


20 

1.86 

1.82 

0.51 

5.97 

10.16 

1.07 

1.05 

4.03 

6.15 


24 

1.86 

1.82 

0.51 

5.97 

10.16 

1.07 

1.05 

4.03 

6.15 


28 

1.86 

1.82 

0.51 

6.04 

10.23 

1.07 

1.05 

4.07 

6.19 


Table 2 gives the percentage of total area occupied by entries 
and the percentage of total area extracted in entries, all for rooms 
25 feet wide. Column 3 gives the percentage of total area in the main 
entry, column 4 the percentage of total area in the cross entries, 
column 5 the percentage of total area in the room entries outside 
the panel, column 6 the percentage of total area in the room entries 
inside the panel, and column 7 the total percentage of area occupied 
by entries. Column 8 gives the percentage of total area extracted 
in main entry, column 9 the percentage extracted in cross entries, 
column 10 the percentage extracted in room entries, and column 11 
the total percentage of area extracted in entries. 

The values in Table 2 are illustrated by Fig. 5 which shows the 
percentage of total area occupied by entries, including the entry pil¬ 
lars, for different numbers of rooms per entry and different lengths 
of rooms. The diagrams are drawn for 25-foot rooms, but, as shown 
in the discussion of the methods of calculation, they would be only 
slightly changed if different room widths were considered. 




































Forf/on of To/o/ Arec? Dei/o/ecf to Fntr/es /nFerCent 


32 


ILLINOIS ENGINEERING EXPERIMENT STATION 



Fig. 5. Percentage of Total Area Occupied by Entries for Eooms 

25 Feet Wide, on 50-Foot Centers 





















































































































PANEL SYSTEM OF COAL MINING 


33 


Column 3 of Table 3 shows the amounts of narrow work in en¬ 
tries. Columns 4, 5, 6, and 7 give respectively the length of main 


Table 3 

Length of Entries and Yards of Narrow Work 


Length of 
Rooms 
(Feet) 

Number of 
Rooms per 
Room Entry 

Yards of 
Narrow 
Work 

Length of Double Entries in Feetl 

Main 

Entry 

Cross 

Entry 

Room 

Entry 

Total 


8 

« 

17192 

2640 

7773 

12215 

22628 


12 

15488 

2640 

5182 

12585 

20407 

200 

16 

13707 

2640 

2591 

12830 

18061 


20 

13707 

2640 

2591 

12830 

18061 


24 

13707 

2640 

2591 

12830 

18061 


28 

13804 

2640 

2591 

12955 

18186 


8 

15333 

2640 

7773 

9772 

20185 


12 

13591 

2640 

5182 

10068 

17889 

250 

16 

11752 

2640 

2591 

10264 

15495 


20 

11771 

2640 

2591 

10264 

15495 


24 

11771 

2640 

2591 

10264 

15495 


28 

11848 

2640 

2591 

10364 

15595 


8 

15333 

2640 

7773 

9772 

20185 


12 

13591 

2640 

5182 

10068 

17889 

300 

16 

11752 

2640 

2591 

10264 

15495 


20 

11771 

2640 

2591 

10264 

15495 


24 

11771 

2640 

2591 

10264 

15495 


28 

11848 

2640 

2591 

10364 

15595 


iThese lengths refer to pairs of entries, not to single entries: i. e., they represent haulage distances 
along the entries. The total length of narrow work for which yardage is paid is therefore double the 
length given, plus the sum of the lengths of cross-cuts. 


entries, cross entries, room entries and total entries, in all cases with¬ 
out entry cross-cuts. It should be noted that these are the lengths 
of double entries and not of single entries; for example, the length 
of the main entry, 2640 feet, is the distance across the tract. 

The total cross entry length does not vary with the length of 
rooms, but decreases with the increase in the number of rooms per 
entry. This decrease is actually more regular than is indicated, be¬ 
cause the table is for a small tract in which a cross entry is occasion¬ 
ally forced outside the boundary by increase of number of rooms 
per entry. 

In the tract considered the total room entry length is the same 
for 250-foot and 300-foot rooms, but is greater for 200-foot rooms. 
If a large area were considered, the lengths for the 250-foot and 300- 
foot rooms would not coincide, but the length for the 250-foot rooms 
would lie between those of the 200-foot and 300-foot rooms. The total 
length of room entries increases slightly as the number of rooms per 
entry increases. 















Percentage of Extraction in Panels, in Entries, and Total Extraction^ 


ILLINOIS ENGINEERING EXPERIMENT STATION 


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To to/ Tx tract ion in FerCent 


PANEL SYSTEM OF COAL MINING 


35 



Fig. 6. Total Percentage of Extraction . 


The decrease in length of cross entries with increase of number 

- . .. 

of rooms per entry ceases at about 16 rooms per entry; Tf a^larger 
area were considered, the cliange would be less abrupt than it is.- "" 


















































































































































36 ILLINOIS ENGINEERING EXPERIMENT STATION 

Table 4 gives the percentages of extraction for all widths of 
rooms considered. The first group of figures in columns 3, 4, 5, 6, 
and 7, gives the percentage of extraction inside the panel for each 
width of room, for each length of room and for each number of rooms 
per entry. The second group of figures, given in columns 8, 9, 10, 
11, and 12, gives the percentage of total area extracted in panels for 
each width of room, each length of room, and each number of rooms 
per entry. In each case this percentage is obtained by multiplying 
the percentage of extraction inside the panel by the percentage of 
area occupied by panels. The values in column 13 give the percentage 
of area extracted in entries outside the panels. 

The third group of figures, given in columns 14, 15, 16, 17, and 
18, gives the total percentage of extraction. This percentage is ob¬ 
tained in each case by adding to the percentage of area extracted in 
panels the percentage of area extracted in entries outside the panels. 

It will be noted that the total percentage of extraction is increased 
by increasing the length of rooms, the width of the rooms and the 
number of rooms per entry. 

The values for total extraction given in Table 4 are shown graphi¬ 
cally by Fig. 6. This set of diagrams shows plainly, in the broken 
lines plotted from the figures in the table, one of the irregularities 
resulting from the use of a small area as a basis for calculation: that 
is, the apparent drop in total percentage of extraction at 24 rooms 
per entry. The percentage of extraction does not actually drop at 
this point, however, the apparent drop being due to the consideration 
of a limited area. Calculations for 25 rooms per entry place the curve 
at its approximately proper position, and the solid lines show this 
position. 

Table 5 shows the percentage of loss inside the panel and the 
percentage of total area lost inside the panels, for all conditions con¬ 
sidered. Columns 3 to 7 inclusive give the percentages of loss inside 
the panel for the different conditions; columns 8 to 12 inclusive give 
the percentage of total area lost inside the panels. These latter figures 
are obtained by multiplying the percentage of area devoted to panels 
by the percentage of loss inside the panels, which is obtained by sub¬ 
tracting the percentage of extraction inside the panel from one hun¬ 
dred. ll 

Table 6 gives the percentages of total area left in pillars outside 
panels; that is, all coal left in the mine except that in room pillars 


PANEL SYSTEM OP COAL MINING 


37 


Table 5 


Percentage Lost in Panels 


Length of 
Rooms 
(Feet) 

Number of 
Rooms per 
Room Entry 

Percentage of Loss 

Inside Panels. 

Percentage of Total Area 

Lost Inside Panels 

20-ft. 

Rooms 

25-ft. 

Rooms 

30-ft. 

Rooms 

35-ft. 

Rooms 

40-ft. 

Rooms 

20-ft. 

Rooms 

25-ft. 

Rooms 

30-ft. 

Rooms 

35-ft. 

Rooms 

40-ft. 

Rooms 


8 

48.88 

41.13 

33.38 

25.62 

17.87 

30.39 

25.57 

20.75 

15.93 

11.11 


12 

49.54 

42.01 

34.48 

26.95 

19.41 

34.64 

29.49 

24.20 

18.92 

13.63 

200 

16 

49.86 

42.44 

35.01 

27.59 

20.16 

38.44 

32.72 

26.99 

21.27 

15.54 


20 

50.05 

42.69 

35.33 

27.96 

20.60 

39.26 

33.49 

27.72 

21.93 

16.16 


24 

50.18 

42.85 

35.53 

28.21 

20.90 

39.37 

33.62 

27.87 

22.13 

16.40 


28 

50.26 

42.97 

36.17 

28.39 

21.67 

39.85 

33.99 

28.68 

22.51 

17.18 


8 

46.75 

39.08 

31.41 

23.74 

16.07 

29.32 

24.51 

19.70 

14.89 

10.08 


12 

47.35 

39.91 

32.48 

25.08 

17.61 

33.52 

28.26 

23.00 

17.76 

12.47 

250 

16 

47.65 

40.33 

33.01 

25.99 

18.38 

37.05 

31.36 

25.67 

20.21 

14.29 


20 W 

:47.82, 

40.57 

33.33 

26.07 

18.73 

37.84 

32.11 

26.38 

20.63 

14.82 


24 'r 

47.961 

40.73 

33.53 

26.33 

19.14 

37.94 

32.23 

26.53 

20.83 

15.15 


281^ 

48.02 

40.85 

33.64 

26.50 

19.33 

38.40 

32.67 

26.90 

21.19 

15.46 


8 

45.25 

37.63 

30.02 

22.40 

14.79 

28.62 

23.80 

18.99 

14.17 

9.35 


12 

45.83 

38.47 

31.11 

23.74 

16.38 

32.73 

27.47 

22.22 

16.95 

11.70 

300 

16 

46.12 

38.88 

31.63 

24.39 

17.15 

36.17 

30.49 

24.81 

19.13 

13.45 


20 

46.29 

39.12 

31.94 

24.77 

17.60 

36.94 

31.22 

25.49 

19.77 

14.05 


24 

46.40 

39.27 

32.15 

25.02 

17.90 

37.03 

31.34 

25.66 

19.97 

14.29 


28 

46.48 

39.38 

32.29 

25.20 

18.11 

37.49 

31.76 

26.04 

20.33 

14.61 


Table 6 


Percentage Lost in Pillars Outside the Panels Except in Entries 


Percentage of Total Area Left in Pillars Outside Panel 
Except Entry Pillars 


Number of 


Rooms 

(Feet) 

Rooms per 
Room Entry 

Main 

Entry 

Barriers 

Cross 

Entry 

Barriers 

Total in 
Entry 
Barriers 

At Ends 
of Panels 

At Sides 
of Panels 

Total 


8 

7.34 

18.41 

25.75 

1.72 

2.15 

29.62 


12 

7.42 

12.96 

20.38 

0.86 

2.43 

23.67 

200 

16 

7.50 

7.82 

15.32 

0.86 

2.67 

18.85 


20 

7.50 

6.48 

13.98 

0.86 

2.72 

17.56 


24 

7.50 

6.48 

13.98 

0.86 

2.72 

17.56 


28 

7.50 

6.48 

13.98 

0.00 

2.74 

16.72 


8 

; 7.34 

18.63 

25.97 

1.72 

1.61 

29.30 


12 

1 7.42 

13.12 

20.54 

0.86 

1.82 

23.22 

250 

16 

► 7.50 

7.92 

15.42 

0.86 

2.00 

18.28 


20 

f 7.50 

6.56 

14.06 

0.86 

2.04 

16.96 


24 i 

L 7.50 

6.56 

14.06 

0.86 

2.04 

16.96 


281 

|7.50 

6.56 

14.06 

0.00 

2.06 

16.12 


8 

7.34 

18.63 

25.97 

1.72 

1.08 

28.77 


12 

7.42 

13.12 

20.54 

0.86 

1.22 

22.62 

300 

16 

7.50 

7.92 

15.42 

0.86 

1.34 

17.62 


20 

7.50 

6.56 

14.06 

0.86 

1.36 

16.28 


24 

7.50 

6.56 

14.06 

0.86 

1.36 

16.28 


28 

7.50 

6.56 

14.06 

0.00 

1.37 

15.43 

























































38 


ILLINOIS ENGINEERING EXPERIMENT STATION 


and entry pillars. Column 3 gives the percentage of total area occu¬ 
pied by the main entry barriers; column 4 the percentage of total 
area occupied by cross entry barriers; and column 5 the percentage 
of total area in all entry barriers, the sum of the two preceding col¬ 
umns. Column 6 gives the percentage of total area left in pillars at 
ends of panels, column 7 the percentage of total area left in pillars at 
sides of panels, and column 8 the percentage of total area left in pillars 
outside the panels except in entries. Column 8 represents the sum 
obtained by adding together the proper figures in columns 3, 4, 6, 


Table 7 

Extraction in Wide Work and in Narrow Work ■ 


Length of 
Rooms 
(Feet) 

Number of 
Rooms per 
Room Entry 

Percentage of Total Extraction 
Obtained from Narrow Work 

1 

Percentage of Total Extraction 
Obtained from Wide Work 

20-ft. 

Rooms 

25-ft. 

Rooms 

30-ft. 

Rooms 

35-ft. 

Rooms 

40-ft. 

Rooms 

20-ft. 

Rooms 

25-ft. 

Rooms 

30-ft. 

Rooms 

35-ft. 

Rooms 

40-ft. 

Rooms 


8 

24.26 

21.47 

19.26 

17.46 

15.96 

75.74 

78.53 

80.74 

82.54 

84.04 


12 

20.55 

18.12 

16.20 

14.65 

13.37 

79.45 

81.88 

83.80 

85.35 

86.63 

200 

16 

17.34 

15.23 

13.57 

12.24 

11.15 

82.66 

84.77 

86.43 

87.76 

88.85 


20 

17.15 

15.06 

13.43 

12.11 

11.03 

82.85 

84.94 

86.57 

87.89 

88.97 


24 

17.19 

15.10 

13.47 

12.15 

11.07 

82.81 

84.90 

86.53 

87.85 

88.93 


28 

17.17 

15.09 

13.46 

12.15 

11.07 

82.83 

84.91 

86.54 

87.85 

88.93 


8 

20.78 

18.57 

16.71 

15.19 

13.93 

79.22 

81.43 

83.29 

84.81 

86.07 


12 

17.32 

15.35 

13.78 

12.51 

11.45 

82.68 

84.65 

86.22 

87.49 

88.55 

250 

16 

14.21 

12.56 

11.19 

10.21 

9.31 

85.79 

87.44 

88.81 

89.79 

90.69 


20 

14.06 

12.43 

11.14 

10.09 

9.22 

85.94 

87.57 

88.86 

89.91 

90.78 


24 

14.10 

12.47 

11.17 

10.13 

9.26 

85.90 

87.53 

88.83 

89.87 

90.74 


28 

14.07 

12.45 

11.15 

10.11 

9.25 

85.93 

87.55 

88.85 

89.89 

90.75 


8 

20.25 

18.06 

16.30 

14.85 

13.63 

79.75 

81.94 

83.70 

85.15 

86.37 


12 

16.74 

14.90 

13.42 

12.21 

11.20 

83.26 

85.10 

86.58 

87.79 

88.80 

300 

-16 

13.72 

12.17 

10.94 

9.94 

9.10 

86.28 

87.83 

89.06 

90.06 

90.90 


20 

13.57 

12.05 

10.84 

9.84 

9.02 

86.43 

87.95 

89.16 

90.16 

90.98 


24 

13.60 

12.08 

10.87 

9.87 

9.05 

86.40 

87.92 

89.13 

90.13 

90.95 


28 

13.57 

12.06 

10.85 

9.86 

9.04 

86.43 

87.94 

89.15 

90.14 

90.96 


Table 7 gives a comparison between the total extraction made 
in narrow work and that made in wide work. Columns 3 to 7, inclu¬ 
sive, give the percentage of total extraction obtained from narrow 
work; that is, from entries and entry cross-cuts for all conditions 
considered. In each case the total extraction, whatever the actual 
figure, is considered 100 per cent. Columns 8 to 12, inclusive, give 
the percentage of total extraction obtained from wide work; that is, 
from rooms, room necks, and room cross-cuts. When these values are 
considered, it should be remembered that the limit between wide 
work and narrow work has been set arbitrarily. It is considered for 

























PANEL SYSTEM OF COAL MINING 


39 


the purpose of these calculations that all workings less than 18 feet 
in width are narrow work and all workings 18 feet or more in width 
are wide work. It is to be noted that the percentage of the total 
extraction obtained from narrow work decreases as the length of 
rooms increases, as the number of rooms per entry increases, and as 
the width of rooms in relation to width of room pillars increases. 

As narrow work is more expensive than wide work, efforts will 
be made to reduce it to the minimum in places where the conditions 
of roof and floor permit. This reduction can sometimes be accom¬ 
plished by increasing the width of entries and entry cross-cuts. Where 
this increase is impossible, the only means of reducing the amount of 
narrow work is by decreasing the length of entries, assuming that 
room cross-cuts and room necks are wide work. This assumption, how¬ 
ever, is not always true. The work of J. C. Quade (see Appendix I) 
illustrates the reduction of narrow work by increase of the width of 
room cross-cuts. 

Summaries of the percentages won and lost in different portions 
of the workings are given in Figs. 7, 8, and 9, which illustrate the 
results with rooms 25 feet wide, and 200, 250, and 300 feet long 
respectively. In each case the total height of the diagram represents 
100 per cent of area. The height from the bottom border to the first 
line^ represents the percentage of total area extracted inside the panels; 
the height from the first line to the second represents the percentage 
extracted in entries outside the panels; the height from the second 
line to the third represents the percentage lost in entries outside the 
panels; the height from the third line to the fourth represents the per¬ 
centage lost in pillars outside the panels; and the height from the 
fourth line to the top of the figure represents the percentage lost inside 
the panels. As these diagrams are based only upon results with 25-foot 
rooms on 50-foot centers, no changes of percentage of extraction are 
involved that are dependent upon change of room width. 

These diagrams illustrate the final disposal of the coal in the 
area considered; they show the amounts won and lost, and the general 
distribution of extraction and losses. The coal extracted comes from 
panels and from entries outside the panels, the larger part coming 
from the panels. As the number of rooms per entry increases, the 
amount of coal taken from the panels increases, but in the example 
considered it remains fairly constant after the number of rooms per 
entry reaches about twenty. 


40 


ILLINOIS ENGINEERING EXPERIMENT STATION 




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Fig. 7. Distribution of Extraction and Loss for Kooms 200 Feet Long, 

25 Feet Wide, on 50-Foot Centers 














































































































7b/^/ /^reo /n Fer Cent 


PANEL SYSTEM OF COAL MINING 


41 



Number of Foom5 per Entry 


Fig. 8. Distribution of Extraction and Loss for Eooms 250 Feet Long, 

25 Feet Wide, on 50-Foot Centers 






































































































































Tofo/ Area /n Cen/ 


42 


ILLINOIS ENGINEERING EXPERIMENT STATION 


Number of Noams per Entry 



'vLost m fiHars outside 




\ w Won In 5/ae Eone/ 5 . 


' Fig. 9. , Disthibijtion op Extraction and Loss for Rooms 300 Feet Long, 

25 Feet Wide, on 50-Foot Centers 







































































































































PANEL SYSTEM OF COAL MINING 


43 


With the increase of number of rooms per entry there is a slight 
decrease in the percentage extracted from entries outside the panels 
and also a slight decrease in the coal lost in entries outside the 
panels, both decreases being due to reduction of area occupied by 
entries. It is shown plainly that the amount of coal lost and won 
in entries is not large in any case. 

One thing clearly indicated is that the increased extraction which 
accompanies increase of number of rooms per entry is due largely 
to a decrease in loss in pillars outside the panels; that is, to decrease 
of space occupied by barrier pillai*s. It is also shown that this 
decrease is much less rapid after rather than before approximately 
16 rooms per entry have been reached and that beyond 20 rooms per 
entry there is very little change. 

The fact that the lines become nearly horizontal after 16 to 20 
rooms per entry have been reached shows that no material increase of 
percentage of extraction can be made by further increasing the number 
of rooms per entry. Comparison of the three diagrams shows also that 
very slight additional extraction can be accomplished by lengthening 
rooms. It follows, therefore, that the only two ways of increasing 
extraction are by increase of ratio of room width to pillar width and 
by extraction of pillar coal. These two methods may be said to reduce 
the loss in room pillars, but by entirely different means. It has been 
proved by experience that attempts to increase room width at the 
expense of pillar width are dangerous, and it is believed that the 
greatest ratio of room width used in the preceding discussion,— 
namely, four to one, considerably exceeds any limit which would or¬ 
dinarily be safe for operation. It therefore follows that increase of 
extraction can be attained only by adopting some method for removing 
pillar coal after the rooms have been driven. 

« 

26. Other Methods of Computation .—It is recognized that the 
inclusion of the main entry and its barrier pillars in the tract con¬ 
sidered gives percentages of extraction that must be changed some¬ 
what if applied to larger areas, because the ratio of barrier pillar to 
total area is greater than would be the case in a larger area. This 
error could be avoided to some extent by choosing the part of the 
mine to be examined so that the main entry would not be included; 
thus the computed extraction would be a little too high. 

Irregularities due to the limiting of the area considered could be 


44 


ILLINOIS ENGINEERING EXPERIMENT STATION 


avoided by a method of computation suggested by C. W. Hippard. 
Instead of a unit area of 160 acres, the area served by a pair of room 
entries with half of the adjoining cross entry and barriers and half 
of the surrounding fire pillars is considered. Such an area, which 
may be called a unit panel, is shown enclosed by dotted lines in Fig. 10. 



Fig. 10. Unit Panel 


A single panel with its proper share of cross entry, barriers, and fire 
pillars is considered a true sample of the mine. The area of the 
tract considered is not constant, but changes with length of rooms, 
width of rooms, and number of rooms per panel. As the proportion 
of the main entry and barriers properly chargeable to this unit area 
changes with the size of the tract considered, it is best not to include 





































PANEL SYSTEM OF COAL MINING 


45 


main entry and barriers in the calculation. Calculated percentages 
of extraction are then a little too high. 

The following computation by this method illustrates the pro¬ 
cedure. The dimensions considered are those given on page 18. 


Area of panel except room entry, (p. 21), 287,500 square feet 
Percentage of extraction in room-and-pillar area, (p. 21), 59.91 per cent 
Area excavated in panel except room entry, 

0.5991X287,500=. 172,241 square feet 

Area occupied by room entry, 

44X675 = 29,700 square feet 
Percentage of extraction in room entry, 

(p. 21), 62.12 per cent 
Area excavated in room entry, 

0.6212X29,700=. 18,450 square feet 

Area occupied by cross entry, 

1^X49X564 = 13,818 square feet 
Percentage of extraction in cross entry, 

(p. 22), 57.48 per cent 
Area excavated in cross entry, 

0.5748X13,818=. 7,943 square feet 

Total area excavated .... 198,634 square feet 

Area of tract considered, 

564X712=401,568 square feet 
Percentage of extraction 


198,634X100 

401,568 


=49.47 per cent 


This result is 3.14 per cent greater than the extraction calculated 
by the method described on pages 18 to 24, the difference being due to 
the exclusion of the main entry and its barriers in the unit panel 
method. Calculations by the latter method with other numbers of 
rooms per entry give the following results: 


16 rooms per entry 
20 rooms per entry 
24 rooms per entry 
28 rooms per entry 


Extraction 
50.98 per cent 
51.96 per cent 
52.64 per cent 
53.14 per cent 


The percentages thus obtained agree closely with those previously 
calculated. 







46 


ILLINOIS ENGINEERING EXPERIMENT STATION 


APPENDIX I 

Cost of Production and the Percentage of Extraction 

IN Fulton County 

Work of J. C. Quade 

An investigation of the percentage of extraction in the Fulton 
County field has been made by J. C. Quade, Chief Engineer of the 
Big Creek Coal Company and of the Saline County Coal Company. 
The results of this investigation are in part reproduced in the follow¬ 
ing pages through the courtesy of Mr. Quade who has reviewed the 
summary. 

These computations were made chiefly to find means of reducing 
the cost of production, the computation of extraction being incidental 
but necessary to the computation of cost. The results show that the 
' highest percentage of extraction accompanied the lowest cost of pro¬ 
duction per thousand tons. 

In making computations of cost no attention was paid to the 
total cost of production, but only to the items which would be directly 
modified by changes of dimensions of workings. The values of these 
were determined in part by the prices fixed in the agreement with the 
United Mine Workers and in part by practice in the Fulton County 
field. 

The items considered in the computation are: 

Yardage paid for narrow work. 

Room turning. 

Switch laying. 

Wood track. 

Props. 

These items are intended to cover labor and materials not directlv 
employed in the extraction of coal. The materials considered are 
those from which little if any salvage is expected. Such large items 
of expense as mining, haulage, ventilation, drainage, interest on capital 
and amortization are omitted because they are little affected by the 
changes contemplated. The expense of maintaining the various items 
considered is small in comparison with the total cost of production, 


PANEL SYSTEM OF COAL MINING 


47 


but the calculation includes those items which are most immediately 
and completely affected by changes in the dimensions of workings. 

The method of computation was determined by the fact that the 
company had an area of 160 acres in Fulton County which was soon 
to be developed. The tract was in the form of a square with public 
roads on two sides, coal owned by the company on the third side, 
and coal not owned by the company on the fourth side. It was there¬ 
fore necessary to leave pillars along three borders but not along the 
fourth. This tract was laid out with two main entries, and with six 
cross entries where 210-foot rooms are considered and seven cross en¬ 
tries where 180-foot rooms are considered as shown in Fig. 11. The 
form of the field and the necessity of leaving boundary pillars in- 



Fig. 11. Map of 160 Acres for J. C. Quade’s Computation 























































































48 


ILLINOIS ENGINEERING EXPERIMENT STATION 


fluenced both the lengths of entries and the number of rooms. The 
coal lying east and west of this tract was developed later; hence two 
pairs of room entries were extended through the boundary pillars on 
each side to become the cross entries of the newer developments. 

Only two lengths of rooms were considered: 180 feet because 
that length was then being used by the company, and 210 feet because 
experience had shown this to be the maximum length for a room which 
could commonly be kept open for the time required to complete ex¬ 
traction without considerable expense for retimbering. 

An analysis of the fixed costs in the district in which the mine 
is located showed that the yardage paid for narrow work in room 
cross-cuts was responsible for a considerable share of these costs. This 
yardage could be eliminated by driving room cross-cuts wider than 
the limit for which yardage is paid, or could be reduced by decreasing 
the length of the room cross-cuts by making pillars narrower. The 
calculations involve both methods. 

The following items of cost are based upon conditions in the 
Fulton County field at the time when the calculations were made. 

Mining rates fixed by agreement between the United Mine 
Workers and Operators. 

Per Yard 


Pick rate, 8-foot entries.$1.82 

12-foot entries .1.24 

16-foot entries.0.00 

Room turning.4.55 

Machine rate, 8-foot entries.1.46 

12-foot entries.1.00 

16-foot entries.0.00 

Room|turning.3.64 


Items fixed by the experience of the company in the Fulton 
County Field. 

Switch laying and ties.$4.00 per room 

Pi’ops. 0.005 per square foot 

Each prop costing $0.06 and supporting an 
average of 12 square feet of roof. 

Wood rails, 1.3 times the length of the room at $22.00 per 1000 board 

feet . . •.6.25 for 180-foot room 

7.45 for 210-foot room 

Track laying and ties.0.10 per foot 

Brushing and timbering entries, approximately $3.00 

per foot for 25 per cent of the length of the entry . . . 0.75 per foot 















PANEL SYSTEM OF COAL MINING 


49 


Some of the figures given would not be applicable at present, 
but the method used can be applied by changing the expense of 
various items to correspond with changes in conditions. 

In computing the production to be expected from different dimen¬ 
sions of workings, it is assumed that 25 cubic feet of coal in place 
are equivalent to one ton, and that 5.70 square feet of area are 
equivalent to a production of one ton if proper allowances are made 
for the thickness of the coal, which averages 4 feet, 10 inches, and 
for the waste which always accompanies mining. It is assumed that 
rooms from adjoining cross entries are driven through until they 
meet and that five cross-cuts are driven in the length of the two 
180-foot rooms and six in the length of the two 210-foot rooms. This 
arrangement accounts for the average number of cross-cuts being 
254 for a 180-foot room. 

The following tables give the essential data on which the cal¬ 
culations are based. Table 8 gives the number of rooms in 160 acres, 
for each room width and for each pillar width, for rooms 180 feet 
long and 210 feet long. The total number of rooms varies less regu- 

Table 8 


Number of Rooms in 160 Acres 


Room 

Width 

(Feet) 

Room 

Length 

and 

Centers 

Pillar Width 


7. 

8 

9 

10 

n 

11 

12 

16 

[20 


180 

1330 

1298 

1232 

1204 

1162 

1120 

1106 

980 

882 

20 

Centers 

26 

27 

28 

29 

(30 

31 

32 

36 

40 


210 

1140 

1104 

1056 

1032 

996 

960 

948 

840 

756 


180 

1298 

1232 

1204 

1162 

1120 

1106 

1050 

952 

840 

21 

Centers 

27 

28' 

29 

30 

31 

32 

33 

37 

41 


210 

1104 

1056 

1032 

996 

960 

948 

900 

816 

720 


180 

1232 

1204 

1162 f 

1120 

1106 

1050 

11036 

938 

840 

22 

Centers 

28 

29 

30 

31 

32 

33 

34 

• 38 

42 


210 

1056 

1032 

996 

960 

948 

900 

888 

804 

720 


180 

1204 

1162 

1120 

1106 

1050 

1036 

994 

896 

826 

23 

Centers 

29 

30 

31 

32 

33 

34 

35 

39 

43 


210 

1032 

996 

960 

948 

900 

888 

852 

768 

708 


180 

1162 

1120 

1106 

1050 

1036 

994 

980 

882 

784 

24 

Centers . 

30 

31 

32 

33 

34 

35 

36 

40 

44 


210 

996 

960 

948 

900 

888 

852 

840 

756 

672 


180 

1120 

1106 

1050 

1036 

994 

980 

952 

840 

784 

25 

Centers 

31 

32 . 

33 

34 

35 

36 

37 

41 

45 


210 

960 

948 

900 

888 

852 

840 

816 

720 

672 


180 

1106 

1050 

1036 

994 

980 

952 

938 

840 

770 

26 

Centers 

32 

33 

34 

35 

36 

37 

38 

42 

46 


210 

948 

900 

888 

852 

840 

816 

804 

720 

660 






























50 ILLINOIS ENGINEERING EXPERIMENT STATION 

larly than the dimensions, because no fractional rooms were considered, 
but only such arrangements of whole rooms as would most nearly 
completely cover the 160-acre tract. 


Table 9 

Area of RoomsI and Tons of Coal per Room2 


Width of 
Rooms 
' (Feet) 

Length 180 Feet 

Length 210 Feet 

Area 

(Square Feet) 

Tons 

Area 

(Square Feet) 

Tons 

20 

3382 

593.33 

3982 

698.60 

21 

3546.5 

622.16 

4176.5 

732.32 

22 

3711 

651.05 

4371 

766.84 

23 

3875.5 

679.91 

4565.5 

800.96 

24 

4040 

708.77 

4760 

835.08 

25 

4204.5 

737.63 

4954.5 

869.20 

26 

4369 

766.50 

5149 

903.33 


INot including cross-cuts. 

25.70 square feet of 4-foot, 10-inch coal per ton, allowing for waste. 


Table 10 

Area of Room Cross-Cuts (per Cross-Cut), Tons of Coal Produced and 

Yardage Cost^ 


Width 

of 

Pillar 

(Feet) 

8-ft. Cross-Cut 

12-ft. Cross-Cut 

16-ft. Cross-Cut 

Area 

(Square 

Feet) 

Tons of 
Coal 
at 

5.70 

Square 

Feet 

per 

Ton 

Yardage 
Cost at 
601 cents 
per Foot 

Area 

(Square 

Feet) 

Tons of 
Coal 
at 

5.70 

Square 

Feet 

per 

Ton 

Yardage 
Cost at 
41 i cents 
per Foot 

Area 

(Square 

Feet) 

Tons of 
Coal 
at 

5.70 

Square 

Feet 

per 

Ton 

Yardage 

Cost 

0.00 

6 

48 

8.41 

$3.64 

72 

12.62 

$2.48 

96 

16.84 


7 

56 

9.83 

4.25 

84 

14.74 

2.89 

112 

19.65 


8 

64 

11.23 

4.85 

96 

16.84 

3.31 

128 

22.46 


9 

72 

12.63 

5.46 

108 

18.94 

3.72 

144 

25.26 


10 

80 

14.03 

6.07 

120 

21.05 

4.14 

160 

28.07 


11 

88 

15.44 

6.67 

132 

23.16 

4.55 

176 

30.88 


12 

96 

16.84 

7.28 

144 

25.66 

4.96 

192 

33.68 


16 

128 

22.46 

9.71 

192 

33.69 

6.61 

256 

44.91 


'20 

160 

28.07 

12.13 

240 

42.10 

8.27 

320 

56.14 



1 Yardage for narrow work, pick rate: 


8 feet wide $1.82 = 60% cents per foot. 
12 feet wide 1.24 =41% cents per foot. 
16 feet wide 0.00=00 cents per foot. 




































































PANEL SYSTEM OP COAL MINING 


51 


Table 9 gives the areas of rooms, not including cross-cuts, and 
the tons of coal per room calculated on the .basis of 5.70 square feet 
per ton. 

Table 10 gives for each cross-cut the area, the tons of coal pro 
duced, and the yardage cost. The number of tons produced is 
calculated from the area on the basis of 5.70 square feet per ton. 
The yardage cost is calculated from the prices fixed in the agree¬ 
ment with the United Mine Workers. Only the rate for pick mining 
was considered as machines were not used much in the district when 
the data were compiled. The ratio between yardage cost for 8-foot and 
12 -foot cross-cuts is the same for pick work as for machine work; there¬ 
fore if the rates for machine work were substituted in place of those 
for pick work in the calculations, the results would show a decrease in 
the total expense, but the percentage of the total expense for narrow 
work saved by the reduction in the amount of this work would remain 
the same. Three widths of cross-cuts were considered: 8 feet, which 
is assumed to be the minimum practical width (this is the minimum 
width for which a yardage price is fixed in the agreement with the 
United Mine Workers); 12 feet, which is considered an average; and 
16 feet, which, according to the agreement, is wide work and does not 
require extra compensation. 

[ 

\ 

Table 11 

Total Cross-Cut Yardage Cost Per Room 


Width of 
Pillar 
(Feet) 

8-ft. Cross-Cuts 

12-ft. Cross-Cuts 

180-ft. Room 

2]/2 Cross-Cuts 

210-ft. Room 

3 Cross-Cuts 

180-ft. Room 

2]/2 Cross-Cuts 

210-ft. Room 

3 Cross-Cuts 

6 

$9.10 

10.92 

6.20 

7'44 

7 

10.63 

12.75 

7.23 

8,67 

8 

12.13 

14.55 

8.28 

9:93 

9 

13.65 

16.38 

9.30 

11,16 

10 

15.18 

18.21 

10.35 

12.42 

11 

16.68 

20.01 

11.38 

13.65 

12 

18.20 

21.84 

12.40 

14.88 

16 

24.28 

29.12 

16.53 

19.84 

20 

30.33 

36.39 

20.67 

24.80 


Table 11 gives the total cross-cut yardage cost per room, obtained 
by multiplying the cost per cross-cut as given in Table 3 by the proper 
number of cross-cuts. 
























52 


ILLINOIS ENGINEERING EXPERIMENT STATION 


Table 12 

Tons of Coal in Cross-Cuts per Room 


Width of 
Pillar 
(Feet) 

180-ft. Room 

2K Cross-Cuts 

210-ft. Room 

3 Cross-Cuts 

8-ft. Cross-Cut 

16-ft. Cross-Cut 

8-ft. Cross-Cut 

16-ft. Cross-Cut 

6 

21.02 

42.04 

25.23 

50.46 

7 

24.58 

49.16 

29.49 

58.98 

8 

28.07 

56.14 

33.69 

67.38 

9 

31.57 

63.14 

37.89 

75.78 

10 

35.08 

70.16 

42.09 

84.18 

11 

38.60 

77.20 

46.32 

92.64 

12 

42.09 

84.18 

50.52 

101.04 

16 

56.15 

112.30 

67.38 

134.76 

20 

70.17 

140.34 

84.21 

168.42 


Table 13 

Cost of Props for Room and Cross-Cuts at One-Half Cent per Square 

Foot, 180-Foot Rooms 


Width 

of 

Room 

(Feet) 

Prop 

Cost 

for 

Room 

Width of Pillar 

6 

7 

8 

9 

10 

11 

12 

16 

20 

Prop Cost for Cross-Cuts per Room 

$0.90 

$1.05 

$1.20 

$1.35 

$1.50 

$1.65 

$1.80 

$2.40 

$3.00 

Prop Cost for Room and Cross-Cuts 

20 

$16.91 

$17.81 

$17.96 

$18.11 

$18.26 

$18.41 

$18.56 

$18.71 

$19.31 

$19.91 

21 

17.73 

18.63 

18.78 

18.93 

19.08 

19.23 

19.38 

19.53 

20.13 

20.73 

22 

18.56 

19.46 

19.61 

19.76 

19.91 

20.06 

20.21 

20.36 

20.96 

21.56 

23 

19.38 

20.28 

20.43 

20.58 

20.73 

20.88 

21.03 

21.18 

21.78 

22.38 

24 

20.20 

21.10 

21.25 

21.40 

21.55 

21.70 

21.85 

22.00 

22.60 

23.20 

25 

21.02 

21.92 

22.07 

22.22 

22.37 

22.52 

22.67 

22.82 

23.42 

24.02 

26 

21.85 

22.75 

22.90 

23.05 

23.20 

23.35 

23.50 

23.65 

24.25 

25.85 


Table 12 gives the amount of cross-cut coal in tons per room, 
obtained by dividing the areas of cross-cuts by 5.70, the number of 
square feet of area equivalent to a production of one ton, and multiply¬ 
ing by the proper number of cross-cuts per room. 







































































PANEL SYSTEM OF COAL MINING 


53 


Table 14 

Cost of Props for Room and Cross-Cuts at One-Half Cent per Square 

Foot, 210-Foot Rooms 


Width 

of 

Room 

(Feet) 

Prop 

Cost 

for 

Room 

Width of Pillar 

6 

7 

8 

9 

10 

11 

12 

16 

2 

Prop Cost for Cross-Cuts per Room 

$1.08 

$1.26 

$1.44 

$1.62 

$1.80 

$1.98 

$2.16 

$2.88 

$3.60 

Prop Cost for Room and Cross-Cuts 

20 

$19.91 

$20.99 

$21.17 

$21.35 

$21.53 

$21.71 

$21.89 

$22.07 

$22.79 

$23.51 

21 

20.88 

21.96 

22.14 

22.32 

22.50 

22.68 

22.86 

23.04 

23.76 

24.48 

22 

21.86 

22.94 

23.12 

23.30 

23.48 

23.66 

23.84 

24.02 

24.74 

25.46 

23 

22.83 

23.91 

24.09 

24.27 

24.45 

24.63 

24.81 

24.99 

25.71 

26.43 

24 

23.80 

24.88 

25.06 

25.24 

25.42 

25.60 

25.78 

25.96 

26.68 

27.40 

25 

24.77 

25.85 

26.03 

26.21 

26.39 

26.57 

26.75 

26.93 

27.65 

28.37 

26 

4k 25.75 i 

26.83 

27.01 

27.19 

27.37 

27.55 

27.73 

27.91 

28.63 

29.35 


Tables 13 and 14 give the cost of props for a room and its cross¬ 
cuts for each width of room from 20 to 26 feet and for each width of 
pillar from 6 feet to 20 feet. The cost in cents is obtained by divid¬ 
ing the cost per prop, taken as six cents, by the area supported by 
one prop, 12 square feet, these being figures based upon the experi¬ 
ence of the company. 


_ Cost per prop _ 

Square feet of area supported 


0 

= — = cent per square foot, or for 1 room 


Number of square feet in room , . . 

--2—- = cost in cents 

In each table the cost of props per room is given at the left, the cost 
of props for cross-cuts is given at the top, and the cost of props for 
the rooms and cross-cuts together is given in the body of the table. 

These tables of prop costs are computed on the assumption that 
all cross-cuts are 12 feet wide. In the comparison of total costs, this as¬ 
sumption introduces a small error because this comparison is be¬ 
tween 8-foot and 16-foot cross-cuts. To obtain correct values it would 
be necessary to make allowance for the error thus introduced by 
















































54 


ILLINOIS ENGINEERING EXPERIMENT STATION 


decreasing the prop cost with 8-foot cross-cuts and increasing it with 
16-foot cross-cuts. The difference between these two costs would ac¬ 
cordingly be decreased, this difference being the saving effected by 
the use of 16-foot cross-cuts. In rooms of 180 feet long with 6-foot 
pillars, the error introduced by the use of this average figure amounts 
to 94 cents per thousand tons. In rooms 210 feet long with 20-foot 
pillars, the error is $2.09 per thousand tons. These errors are the 
extremes, and the errors when other dimensions of rooms and pillars 
are used lie between these two. Since the pillar width selected as the 
best was small,—^viz., 8 feet, the effect of the assumption of 12-foot 
cross-cuts was small. 

The specimen computations given show the methods employed. 
All essential data are contained in the preceding tables and the cal¬ 
culations involve only the arrangement of these data in such form 
as clearly to represent the facts and permit comparisons between per¬ 
centages of extraction and costs of production for different dimen¬ 
sions of rooms. 

SPECIMEN COMPUTATIONS 


Coal Produced 
Rooms and Cross-Cuts 

Room width.20 feet 

Room length. 210 feet ' 

Pillar width.6 feet 

Total number of rooms in 160 acres. 1140 

Room coal. 698.60 tons 

Coal from 8-foot cross-cuts. 25.23 tons. 


Total coal from room and 8-foot cross-cuts . . . 723.83 tons 

Coal from additional 8-feet of cross-cuts. 25.23 tons 


Total coal per room and 16-foot cross-cuts . . . 749.06 tons 


Coal from 160 Acres 

Total room coal = 698.60 XI140= . . . . 

Total coal from 8-foot cross-cuts = 25.23 XI140 = 
Coal from main entry and cross-cuts 
Coal from cross entries and cross-cuts 

Total. 

Additional coal from 16-foot cross-cuts . 


Tons 
796,404 
28,762 
16,716 •- 

47,836 

889,718 
28,762 ’ ' 


918,480^ 


Grand total , 
















PANEL SYSTEM OP COAL MINING 


55 


Cost and Saving 
Fixed Room Charges per Room 


Room turning.$ 4.55 

Switch-laying and ties. 4 qq 

Wood rails. 7 4 g 

$16.00 

Props per room and 8 -foot cross-cut.21.00 

$37.00 

Room cross-cut yardage.10.92 

Total for room and cross-cuts.$47.92 


Total Fixed Room Charges per 160 Acres 

Room turning; switch laying and ties; wood rails, props = $37.00 XI140 = $42,180.00 
Room cross-cut yardage 10.92X1140= 12,448.80 

Total fixed room charges.$54,628.80 

Saving by making cross-cuts 16 feet wide. 

. . . $12,448.80 = 22.79 per cent fixed room charges with 8 -foot cross-cuts 


Total Cost for Items Considered 


Total fixed room charges.. ’. 

Main entry and cross-cuts, 

11,910 feet narrow work at $0.61 per foot.. . 

Cross entries and cross-cuts, 

34,080 feet narrow work at $0.61 per foot. 

Track laying. 

Brushing and timbering. 

Total cost for 160 acres. 

Total cost for 160 acres with 16-foot room cross-cuts, 
118,178.70-12,448.80=. 


$ 54,628.80 

7,265.10 

20,788.80 

4,176.00 

31,320.00 

$118,178.70 

$105,729.90 


118 178 70 

Cost per 1,000 tons with 8 -foot room cross-cuts J ‘ = 

889.718 


Cost per 1000 tons with 16-foot room cross-cuts 


105,729.90 


918.480 

Saving per 1000 tons with 16-foot room cross-cuts* . 


132.83 

115.11 

17.72 


*The cost per 1000 tons mined is less by one method than by the other, but the 
quantity of coal considered is greater in the case of 16-foot room cross-cuts by the 28,762 
tons gained in the additional 8 feet of cross-cut width. 























56 


ILLINOIS ENGINEERING EXPERIMENT STATION 


The accompanying sets of diagrams, Figs. 12 and 13, show the 
most important points in connection with the percentage of extrac¬ 
tion and the cost of production, so far as the latter is determined 
by the limited elements considered, for all room widths from 20 to 
26 feet and for pillar widths of 6, 9, 12, 16, and 20 feet with 210-foot 
rooms and for 6-foot pillar widths with 180-foot rooms. 

Three diagrams in each set are concerned with quantity of pro¬ 
duction. Diagram A gives the number of rooms in 160 acres; diagram 
B, the amount of coal produced per room and cross-cut; and diagram 
C the total amount of coal produced. This total production includes, 
not only coal taken from rooms and their cross-cuts, but also coal taken 
from entries and entry cross-cuts. 


‘o 


I 


1 

<o' 

I 


950 

idO 

' Fooms- 

6'PH 

tars 


900 

C _ 

7^ 





850 

Tvi 

‘ 

Ota/ 

Coa 

/ Fr 

oduc 

:ed^, 

L 

800 

%Ar 

ea i 

fxtr 

acte 

d 

60 

750 






55 

700 






50 




100 

E 






/ 






50 

^C05t > 
1 

oer 

_ 

moo 

_ 

Ton 

_ 

s 

_ 

0 

F-Shi/ino perJ00b Tons 

—" 1 1 1 1 1 — 



1000 


500 


^Number of ffooms- 


6 . 


■Coal per ffoom 
I I I 
0 20 2/ 22 23 24 25 26 










‘O 

<o' 


950 


900 


850 


800 


750 


700 


C 




‘^5 


Totaf CoaJ f^roducelf 

65 


-% Area Axtracred 


60 


55 


/ r 

^/O ffooms-6 FiUars 


I 

•K 


/oo 

- 1 

E 

r— - 1 

Oast 

— 

per 

/OOl 

9 To/ 

15 

50 







0 

ESaFnp 

'Fp 

/OO 'O To/ 
— 1 

15 


/ooo 

A / 

Mu/r, 

ber 

of Foorr. 

5 

500 

E 


Coa, 

f per Fo( 

om 

0 2 

O 2 

■ 

/ 22 23 24 25 26 


Widfh of ffooms /n Feet 


Width of ffoomo in Feet 


Fig. 12. Number of Booms per Entry, Coal per Boom, Total Coal from 
160 Acres, Percentage of Area Excavated, Cost per 1000 Tons, 

Saving per 1000 Tons 






































































































Tons,/fooms Do/fars Coa/ /n /OOO Tons Tons.ffooms Do/lars Coo/ /n /OOP Tons 


PANEL SYSTEM OF COAL MINING 


57 


950 

RfO' Ropms- 

_1_L . 

9'Rlllar^ 

/ 

' 75 

900 

%Area 


uc/t 

'5CJ 

70 



850 


C _ 
fa! ^ 

foal 

Pro 

duct 

'd 65 

800 

To 


60 

750 






55 

700 






50 




iOO 

5 ^ C 

05 / ^ 

— 

oer 

/OO 

0 To 

ns 

50 

A. 

0 


'Rg / 

oer 

Vi 

^ To ? 

IS 

1 


1 


—^^^— r~ 

^Number of f^ooms 



500 


o zo 


".Coo/ per ffoom, 

II I I 

2 / 22 23 25 26 


Wic//f) of ffoom5 in Feet 


<0 




950 

R/p RpomspR Pillar 

— 

75 

900 

^ Ar 

r 1 ^ 

'eo Rx/radec 

d^ 

850 

D 





.-'''TS 

800 

C 

~x^ 





60 

750 

To 

ta/ 

Toai 

Pro 

duct 

^d 

55 

700 






50 






iOO 


Cos/ 

— 

per 

IWo 

Ton 

5 

50 

0 

L 


oer j 

'OOO 


5 

P 






<o 

I 

I 


iooo y/fumber of ffooms 



0 20 2 / 


^oo/^ per^ Room. 

22 23 24 


26 26 


Wid/fi of Rooms in Reef- 


R/0 ffooms-16 Pillars 


950 


900 


75 


70 


S 50 % Area Rx/rocfed 



too 


50 


R 

0 


R 

—p 







'os 7 

per 

— 

1000 

— 

Ton^ 

T 

— 

^Cai/i'ng per IOOO Jons^ 


iOOQ 


B, /Coa/per Room 



500 


Number of Rooms- 


Wid/h of Rooms in Reef 


‘o 

I 

Q 


<o 


I 


I 

‘o' 


950 

— 

C'R 

— 

ooms 

-7" 

-20/ 

— 

T//or 

— 

75 

900 






70 

850 






65 

800 

% 

Are 

a Rx 

/roc 

ied^ 

60 

Z> 

750 


fa! ^ 

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pro 

duc( 


C, 

700 

'/To 




50 


iOO 


50 


T~\ 

—Cost per iOOO Tons 

R ' ' ' ' 

Sai/i'ng per /OOO Tons, 

I ^ M I^L 


iOOO 


500 




Coa/ per Room 


umber of Rooms 


0 20 2 / 


22 


23 24 25 26 


W idt/i of Rooms in Reef 


Fig. 13. Number of Booms per Entry, Coal per Boom, Total Coal from 
160 Acres, Percentage of Area Excavated, Cost per 1000 Tons, 

Saving per 1000 Tons 


Per Cent of To/a/ Area Rer Cent of To/a/ Area 










































































































































































































































58 


ILLINOIS ENGINEERING EXPERIMENT STATION 


Diagram D shows the percentage of extraction, based on the area 
excavated instead of on the number of tons produced as calculated 
by Mr. Quade, in order that this portion of the discussion may be 
brought into direct comparison with the preceding part of the bul¬ 
letin. The values for the percentage of extraction on the area basis 
are slightly higher than they would be if computed from tonnage 
produced because of the waste in mining and the presence of slips 
and horse backs. If these losses did not exist, the values of the per¬ 
centage of extraction obtained by the two methods would be the same, 
because the entire thickness of the coal bed is extracted. A compari¬ 
son of these two methods in rooms 20 by 210 feet with 12-foot pillars 
and 16-foot cross-cuts gave an extraction on the basis of tons pro¬ 
duced of 61.05 per cent and on the basis of area excavated of 67.28 
per cent. 

The diagram for total output is irregular, because its shape is 
determined by that for the number of rooms. This number does not 
change uniformly with change of width of rooms, but, for each set 
of dimensions, the number of rooms was selected which was most 
suitable for working out the 160-acre tract to be developed. The 
total output is the sum of the tonnage of coal produced in rooms and 
cross-cuts, and in, entries. Since the output from entries varies only 
with the number of cross entries which in turn is affected by a 
change in the length of rooms, the total output varies only with the 
number of rooms or with the output from a room and its cross-cuts. 
The latter quantity varies regularly with the change of room width, 
and therefore irregularities in the total output are entirely due to 
irregularities in the number of rooms. The curve for total output 
is drawn to a scale which makes its irregularities more prominent 
than those in the curve for the number of rooms. 

Diagram E shows the cost per thousand tons for the limited 
number of items considered. The line drops as that showing total 
output rises, thus showing that the cost of production decreases as 
the output from a given area increases. 

Diagram F shows the saving per thousand tons accomplished by 
increasing the width of room cross-cuts from 8 feet to 16 feet, and 
eliminating room cross-cut yardage. Mr. Quade’s computations were 
made with the object of determining this saving, and the adoption of 
the dimensions indicated by these calculations as being most economi¬ 
cal has resulted in very large reduction in the cost of producing coal. 


PANEL SYSTEM OF COAL MINING 


59 


The dimensions selected were; room width 24 feet, pillar width 8 feet, 
cross-cut width 16 feet. The diagrams show that the cost would be 
lower and the extraction higher if narrower pillars could be used, but 
it was not practical to make them less than about 8 feet in width. 
This width is, however, necessary only near the entries; the pillars arc 
made gradually narrower towards the ends of the rooms, the percent¬ 
age of extraction being thus increased. The extraction in these mines 
since the adoption of the new dimensions is between 70 and 75 per 
cent. 

For purposes of comparison one set of diagrams is given which 
shows, for 180-foot rooms, the same items of production and cost as 
are given for 210-foot rooms. At the time when the computations 
were made rooms were being driven 180 feet long. The total output 
for the two lengths of rooms differs only slightly, but the cost of 
production is lower with the 210-foot room; hence that length was 
adopted as a standard. 

The diagrams in Fig. 14 show the production of coal from dif¬ 
ferent parts of tlie workings and emphasize the increase of produc¬ 
tion with increase of room width. Diagram A shows the production 
from rooms and 8-foot cross-cuts. Diagram B shows the sum of the 
tonnage of room and cross-cut coal and entry coal, the space between 
A and B representing the entry coal. The space between B and C 
shows the additional coal taken from 16-foot cross-cuts; therefore C 
shows the total coal produced from 160 acres with the longer dimen¬ 
sion. 

Fig. 15 is a graphical summary of costs and output for rooms 24 
feet wide and 210 feet long. Diagrams A, B, C, and D show the effect 
of increase of pillar width on the tonnage produced. On these dia¬ 
grams, A shows the number of rooms in 160 acres; B shows the output 
from rooms and 8-foot cross-cuts; C shows the additional output 
from entries; and D shows the additional output from the extra width 
of room cross-cuts. The diagram shows the decrease of output result¬ 
ing from the decrease in the number of rooms, which accompanies in¬ 
crease of pillar width. 

The items of cost considered in the investigation are shown in 
zones, of which the first is yardage cost for the main entry, the second 
yardage cost for the cross entries, the third track-laying cost for 
entries, the fourth brushing and timbering costs for entries, the fifth 
fixed room charges, and the sixth yardage cost of 8-foot room cross-cuts. 


60 


ILLINOIS ENGINEERING EXPERIMENT STATION 



s'uo2 000/ u/ /ooj 




<0 

c> 

I 

s 


w 

o 







77 


r 







1 

( ^ 

N- 




Y 










1 














'O 

0 \ 














s 



\ 

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_v.. 

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1050 

moo 

< 5 ^ 

006 

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<10 

600 

750 

700 

650 

600 

Ci 

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*0 



S'UOJ 000/ U/ p^^':yy>pjy 2 /ooc^ 


s 

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I 



000/ P^J^oj^yj /i^oj 


Fig. 14. Production from Eooms, Entries, and from Additional Cross-cut 



































































































PANEL SYSTEM OF COAL MINING 


61 


\ 


IZOO 
















uoo 

Wt 

'M 



if 


m 

w 


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m 


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ges- 


700 


ll 

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600 

1 

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h 

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1 

dWA 

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PP 

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sp 

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one 

\, / j // 

^ / in 

loen 

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400 


1 

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y/AA 

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1 


i 


300 

i 

ll 



m 



P 

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fc 

desp 

/aZ// 


200 




/y^/ 


1 

w 

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i 

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t)^/ 

(S/y, 

wt 

a/h 


PP 

'iCho/yes^ 



I' 

II 

‘0 

<S 


F///ar Widths in Wee t 

Fig. 15. Suminiary of Costs and Output for Rooms 24 Feet Wide and 
^ -iii ■ 210 Feet Long 


The first four items change only when change in the length of rooms 
results in change of number of cross entries and therefore of total 
length of entries. The fifth item, fixed room charges, includes room 
turning, switch laying and ties, wood rails, and room props. The 
first three subdivisions change only with the number of rooms; the 
last increases with the width of rooms but decreases with their num¬ 
ber. The sixth item, yardage cost of 8-foot cross-cuts, increases with 
pillar width because of the increased length of the cross-cuts. It 
is this last item of cost which is eliminated by increase of cross-cut 
width to 16 feet, leaving the line M M' as the indication of total cost. 

Some of the charts prepared by Mr. Quade are reproduced with 
some modification in Figs. 16, 17, and 18 to show more fully his 
method of presenting his conclusions. 

Fig. 16 shows the effect of changes in cross-cut width on yard¬ 
age cost for room cross-cuts and the amount of coal produced from 

















































































52 


ILLINOIS ENGINEERING EXPERIMENT STATION 


them. The diagrams are based on 7-foot pillars with three cross¬ 
cuts per pillar. The arrangements of cross-cut widths in each 
pillar are: three 8 feet wide; one 8 feet and two 12 feet; three 12 
feet; one 8 feet, one 12 feet, and one 16 feet; two 12 feet and one 16 
feet; one 12 feet and two 16 feet, and three 16 feet. In the final 
computation of possible reductions of cost the only widths considered 
were 8 feet and 16 feet. 

Fig. 17 gives in detail the cost per thousand tons as modified 
by certain changes in length and width of rooms, room pillars, en¬ 
tries, and room and entry cross-cuts. 

The width of rooms considered, 25.36 feet, was the actual average 
made by 8 cuts of a breast-type chain coal cutting machine. This 
machine is commonly called a 3-foot machine, but the actual cut 
slightly exceeded this width. The costs of the various items considered 
are shown by the widths of the shaded bands, while the solid line A B 
shows the saving per thousand tons accomplished by tlie use of the 



Fig. 16. Effect of Changes in Cross-cut Width on Cost of Cross-cuts and 

Coal Produced 






















































































PANEL SYSTEM OP COAL MINING 


63 



^ Rms-33fr ^ /fms. 33ft ^ 


IdOfr. by 33.36fr. 
dfr. ffm. C. Cut. 

dft £ntry 
Qft Ent. C. Cut 


310 ft. by3536ft 
dft f^m. C Cut 
dft £ntry 
dft dnt C. Cut 


ZlOft. by 35.36ft 
/6ft Rm. C. Cut 
dft Rntry 
dft dnt C.Cut 


3/Oft by353bft 
/6 ft Rm. C Cut 
t3ft. Entry 
/3ft. EntC.Cuf 


Fig. 17. Certain Fixed Charges per 1000 Tons, Saving per 1000 Tons, Total 

Output from 160 Acres 


different changes in dimensions specified. The solid line C D shows 
the total coal produced from 160 acres with the same dimensions. 

Fig. 18 is a summation of the items of room and room cross-cut 
costs considered and of total extraction and cost for 160 acres. This 
figure permits comparisons between results obtained by using different 
dimensions and shows the point of lowest cost and highest extraction. 
As in Fig. 14, room widths of 22.2 feet and 25.36 feet are due to the 
width of cut of the breast-type of coal cutting machines. The lower 
shaded areas show the cost per room for the various items considered 
as fixed room charges. Room turning and switch costs per room are 
not affected by any changes of dimensions. Wood rail cost increases 
with the length of rooms. Prop cost increases with both length and 
width of rooms. Cross-cut yardage cost is affected by room length, 



















































Rooms m lO's /60 Acre Cost /n ^/,000 
Room Costs m Do/fars Tons m /0.000's Cost per /OOO Tons /n Do//c7rs 


64 


ILLINOIS ENGINEERING EXPERIMENT STATION 



^/OT/ Rooms /dOft Rooms 

Width TO TT TTT T5.36 T3.36 TO TTZ T4- T5.36 ft 

Centers26 Z8 30 3T 34 Td 30 32 34 ft 

Fig. 18. Summation of Fixed Charges and Output for 160 Acres 



























































































PANEL SYSTEM OF COAL MINING 


65 


which determines the number of cross-cuts, by cross-cut width and 
pillar width. The upper shaded areas show the difference in total 
cost per thousand tons, including entry costs, which results from the 
use of 8-foot and 16-foot room cross-cuts. The solid lines A B and 
A'B'show the total coal produced from 160 acres; C I) and C'D'show 
the number of rooms in 160 acres; EF and E' F' show the total cost 
for 160 acres wdien 8-foot cross-cuts are used. 

The low^est total cost for 160 acres is shown to be reached with 
210-foot rooms 25.36 feet wide on 34-foot centers, but the lowest cost 
per thousand tons and the highest extraction for 160 acres are shown 
to be reached with rooms of the same dimensions on 32-foot centers. 
Because of the common tendency of the miner to make his room some¬ 
what wider than is planned, the latter dimensions might be approxi¬ 
mately reached in practice if rooms were planned 24 feet wide on 32- 
foot centers. These dimensions, shown by Mr. Quade’s w^ork to be the 
best, were adopted for the company’s mines in Fulton County with 
the result that the cost of producing coal was materially reduced. The 
percentage of extraction was raised from about 58 per cent to between 
70 and 75 per cent which is unusually high for Illinois. 


66 


ILLINOIS ENGINEERING EXPERIMENT STATION 


APPENDIX II 

Extraction at Dewmaine 
Work of G. E. Lyman 

The results obtained with different dimensions of rooms in the 
Williamson County mines of the Madison Coal Corporation are shown 
in the following sketch and notes prepared by G. E. Lyman, for¬ 
merly Chioi Engineer and now General Superintendent of that com¬ 
pany, and are published here with his courteous permission. The 
sketch. Fig. 19, shows the plan of operation followed at Dewmaine, 
north of Carterville. The only changes from the dimensions shown are 
in the width of room pillars, the two widths being 20 feet and 11 
feet. The plans considered and compared, with each pillar width, 
involve the extraction of different quantities of pillar coal after the 
rooms have been finished. 

The area considered is a restricted one, consisting only of a cross 
entry and a portion of the rooms turned from it. The tract'con- 



Fig. 19. Dimensions of Rooms and Cross Entries at Dewmaine 


































































PANEL SYSTEM OF COAL MINING 


67 


sidered is 640 feet wide by 1360 feet long and has an area of 870,000 
square feet. 

The following notes give the results of experience with dilfer- 
ent dimensions of rooms and the extraction of different amounts of 
pillar coal. With each of the two pillar widths different amounts of 
coal were extracted. With rooms 20 feet wide on 40-foot centers, 
plan No. 1, shown in white, gave the following extractions: 


Rooms 

Cross-cuts 

Entries 

Entry cross-cuts 


Square feet 
68X5725 = 389,300 
4X68X 400 = 108,800 
2X10X1360= 27,200 
21X 200 = 4,200 


Total area excavated 


(60.7 per cent) 529,500 


The experience of the company thus far indicates that workings 
with these dimensions will stand indefinitely except where soft mud 
or quicksand predominates in the cover. 

Plan No. 2 involves the driving of additional cross-cuts in the 
room pillars after the room has been completed. These additional 
cross-cuts are shovm by the dotted areas in the figure. The additional 
area extracted is: 

3X68X400 = 81,600 squareJeet 

Total area excavated.(70.2 per cent) 611,100 

Experience indicates that squeezing will occur in rooms, but 
that the entry stumps will protect the entry so that it will not be 
closed. More or less water will follow the squeeze. The surface will 
subside gently to a depth of 2 feet to 4 feet in the center of the area. 

Plan No. 3 involves the driving of additional cross-cuts in the 
room stumps and chain pillar, while retreating, as shown by the 
hatched areas. The additional area excavated is: 

Square feet 

Room cross-cuts.68 feet X400 feet = 27,200 

Entry cross-cuts.20 feet X400 feet = 8,000 

Total area excavated. (72.4’per]cent) 646,300 

The results, as far as subsidences are concerned, are practically 
the same as those obtained by following plan No. 2, except that the 
entry is closed by the squeeze and more water enters the mine. The 
surface subsidence is practically the same as in plan No. 2. 













68 ILLINOIS ENGINEERING EXPERIMENT STATION 






Plans Nos. 4, 5, and 6 apply to the same method of working, but 
with room pillars only 14 feet wide which make 80 rooms in a block 
640 feet by 1360 feet. 

Plan No. 4 involves excavation of the following areas: 


Square feel 

Rooms. 80 X 5725 = 458,000 

Room cross-cuts. 80X4X280= 89,600 

Entries. 2X10X1360= 27,200 

Entry cross-cuts. 21X200= 4,200 

Total_[area excavated _.(66.5 per cent) 579,000 


When this plan is followed, scpieezing occurs in a room a few 
months after the first working and more or less water enters the 
mine. The surface subsidence is about the same as in plan No. 2. 

Plan No. 5 involves the driving of additional cross-cuts, as in 
plan No. 2, and the additional area excavated is: 

Square feet 

Cross-cuts. 3 X 80 X280 = 67,200 

Total area excavated.(74.2jper cent) 646,200 

The results are practically the same as those obtained by following 
plan No. 2, except that more water enters the mine and the sub¬ 
sidence of the surface is deeper. 

When additional cross-cuts are driven in room and entry re¬ 
treating, as shown by the hatched areas, in plan No. 6, the additional 
areas excavated are: 

Square feet 

Room cross-cuts.80 feet X280 feet = 22,400 

Entry cross-cuts.. 20 feet X400 feet = 8,000 

Totaharea'excavated.(77.7^'per^cent) 676,600 

In this case the entire area squeezes, and a large quantity of water 
enters the mine. The surface subsidence extends over the whole area 
and is greater than with any of the other plans. 

In the Dewmaine fields it has not been found practical to 
apply any plan except No. 1 until a considerable portion of the 
mine is ready for abandonment. Slight changes in the projection, 
however, are made when changes in physical conditions make them 











PANEL SYSTEM OF COAL MINING 


69 


advisable. Rooms are driven 20 feet wide, but pillars are sometimes 
reduced to 18 feet and entries are made either 10 or 12 feet wide. 

In this field a great deal of trouble has been caused by the entry 
of water whenever the extraction of too much coal disturbed the 
overlying strata. Since plan No. 1 alone permits the indefinite sus¬ 
taining of the overlying material, it is the only one which can be 
followed without entailing a great expense for handling water. Ex¬ 
traction is therefore limited to about 60 per cent of the panels or 
blocks, and must be considerably less when considering the whole 
mine. The calculated percentages of extraction given on page 34 for 
rooms and pillars of the same ratio of width,— namely, 25-foot rooms 
with 25-foot pillars, indicate that the total extraction is about 10 
per cent less than the extraction in the panel area. It is therefore 
probable that the total amount of coal extracted in the mine as a whole 
is about 50 per cent. At various times plans No. 2 and No. 3 have 
been tried in limited areas, but trouble has always been caused by 
squeezes and inflow of water. 

At the present time mining at No. 8 has proceeded far enough to 
permit the application of plan No. 3 in working from the boundary 
toward the shaft. The additional recovery will probably make the 
total extraction for the entire mine about 60 per cent. 

Mr. Lyman points out that both the depth of cover and the 
nature of the ground vary considerably within short distances in the 
district referred to and that different results might be obtained 
within a short distance of the mine mentioned. 


70 


ILLINOIS ENGINEERING EXPERIMENT STATION 


APPENDIX III 
Work of J. C. Gibson 

J. C. Gibson of the Standard Engineering Company of Diiqnoin 
has developed a method for calculating the percentage of extraction 
and the future life of a mine by which it is possible to indicate the 
parts of the workings in which the losses occur. The following 
description of procedure is published through the courtesy of Mr. 
Gibson. 

When this method is applied, a tracing of the workings is made 
showing the outlines of groups of rooms, entries, barrier pillars, and 
lost areas. In the tracing these separate portions are given distinc¬ 
tive colors in order to prevent any possible confusion. Each area is 
then measured. This measurement can best be done with a plani- 
meter, but very close approximation to the correct areas can be at¬ 
tained by measuring with a scale, especially if the outlines are not 
very irregular. 

The application of this method to a part of a mine is shown in 
Fig. 20. The sums of the areas of the different portions in the entire 
mine are as follows: 

Areas worked out (Acres) Percentage of Total Area 


Rooms and pillars. 

157.16 

59.76 

Entries. 

62.40 

23.73 

Lost coal. 

3.44 

1.30 

Barriers. 

40.00 

15.21 

Total area covered by workings. 

} 


with exception of the shaft pillar 

263.00 

100.00 



Tons 

Room coal produced .... 


. . . . 1,421,023 

Entry coal produced .... 


. . . . 378,744 


Total coal produced, not including coal taken from the shaft 

pillar in driving the bottom. 1,799,767 


The tonnage produced from entries was calculated from the 
length, width and height of the entries and the weight of the coal 
per cubic foot, a method permissible when entries are driven with 










PANEL SYSTEM OF COAL MINING 


71 



Losr Coa/ Rooms & Pillars _ Pntne. 


Banner Pillars 


Fig. 20. Portion of Mine as Mapped by J. C. Gibson 












































































































































































72 


ILLINOIS ENGINEERING EXPERIMENT STATION 


careful adherence to the projected dimensions. The tonnage pro¬ 
duced from other workings is the difference between total output and 
entry coal. 

The average thickness of coal being 9.4 feet and the weight per 
cubic foot 81.25 pounds, the amount of coal originally present per 
acre was 


43,560X9.4X81.25 

2,000 


16,634 tons 


The area worked over by rooms and pillars is 157.16 acres. The 
coal originally present in the room and pillar area was 157.16 X 
16,634 == 2,614,199 tons; and the percentage of extraction in the 
territory occupied by rooms and pillars was 


1,421,023X100 

2,614,199 


= 54.36 per cent 


The entries occupied 62.40 acres, and the coal originally present 
was 62.40 X 16,634 = 1,037,961 tons. The percentage of extraction 
in territory occupied by entries was 


378,744X100 

1,037,961 


= 36.49 per cent 


The coal originally present in the whole area was 263 X 16,634 
= 4,374,742 tons and the percentage of extraction over the whole area 
worked out was 


1,799,767X100 

4,374,742 


= 41.14 per cent 


Since the thickness of the bed is 9.4 feet and the height of en¬ 
tries only 7 feet, the percentage of area excavated in entries is — 

7 

of the percentage of coal extracted. 

9.4 

X 36.49 per cent = 49.00 per cent 

The data given do not provide a basis for the calculation of 
percentage of area worked out in the room-and-pillar blocks, because 
some of the top coal was taken. If no top coal had been taken, the 







PANEL SYSTEM OF COAL MINING 


78 


percentage of area worked out in the seven feet of coal being mined 
would be equal to the percentage of coal produced from that seven 
feet. The amount of coal originally present in the areas occupied 
by rooms and pillars in a thickness of seven feet was 


43,5G0 X7 X81.25 X 157.16 
2000 


1,946,799 tons 


As the coal taken out from these areas was 1,421,023 tons, the 
percentage of area excavated would have been 73.0 per cent if a thick¬ 
ness of onlv^ seven feet had been worked. 


1,421,023X100 

1,946,799 


= 73.0 per cent 


If all the top coal had been taken down to a height of 9.4 feet, 
the percentage of area worked out would be the same as the per¬ 
centage of coal produced when the thickness of 9.4 feet is considered, 
—that is, 54.36 per cent. Since some top coal was left, the percentage 
of area worked out must have been greater than 54.36 per cent and 
less than 72.2 per cent in order to give this percentage of extraction; 
however there are no data from which accurately to calculate the 
percentage. 

In some mines where the only “solid” coal produced is top coal, 
all the remainder being known as “machine” coal, it would be pos¬ 
sible to get from the books of the coal company the number of tons 
of solid coal paid for,—that is, the top coal. Then the percentage 
of area worked out in rooms could be determined from the tonnage 
produced. 

It is claimed by Mr. Gibson that given the data on a number of 
mines in the preceding form, comparisons may be made and possibly 
much valuable information obtained. For example, mines in which a 
high percentage of extraction had been obtained in the room-and- 
pillar areas would indicate the practice to be followed in planning a 
new operation, provided, of course, that the history of those mines 
showed their practice to be satisfactory; mines in which the smallest 
percentage of coal had been lost in barrier pillars, provided the 
barriers had proved sufficient, would indicate the dimensions of barriers 
for use in new operations; and mines having the smallest ratio of en¬ 
try area to room area would suggest efficient methods of developing 
a property. 




74 


ILLINOIS ENGINEERING EXPERIMENT STATION 


Thus, from a number of plans of actual operations, might be de¬ 
veloped a composite plan more efficient than any of those studied. It 
is evident that the two sets of percentages, those of the entire coal seam 
and those of the number of feet of the seam worked, will enable com¬ 
parisons to be made with most of the properties studied. 


PUBLICATIONS OF THE ILLINOIS COAL MINING INVESTIGATIONS 


Bulletin 1. Preliminary Report on Organization and Method of Investigations. 
1913. None available. 

Bulletin 2. Coal Mining Practice in District VIII (Danville), by S. O. Andros. 

1913, None available. 

Bulletin 3. Chemical Study of Illinois Coals, by S. W. Parr. 1916. Twenty-five 
cents. 

Bulletin 4. Coal Mining Practice in District VII (Mines in bed 6 in Bond, Clin¬ 
ton, Christian, Macoupin, Madison, Marion, Montgomery, Moultrie, Perry, Randolph, St, 

Clair, Sangamon, Shelby, and Washington counties), by S. O. Andros. 1914. Free upon 
request. 

Bulletin 5. Coal Mining Practice in District I (Longwall), by S. O, Andros. 1914. 
None available. 

Bulletin 6. Coal Mining Practice in District V (Mines in bed 5 in Saline and 

Gallatin counties), by S. O. Andros. 1914. Free upon request. 

Bulletin 7. Coal Mining Practice in District II (Mines in bed 2 in Jackson 

County), by S. O. Andros. 1914. Free upon request. 

Bulletin 8. Coal Mining Practice in District *VI (Mines in bed 6 in Franklin, 

Jackson, Perry, and Williamson counties), by S. O. Andros. 1914. Free upon request. 

Bulletin 9. Coal Mining Practice in District III (Mines in beds 1 and 2 in Brown, 

Calhoun, Cass, Fulton, Greene, Hancock, Henry, Jersey, Knox, McDonough, Mercer, Morgan, 
Rock Island, Schuyler, Scott, and Warren counties), by S. O. Andros. 1915. Free upon re 
quest. 

Bulletin 10. Coal Resources of District I (Longwall), by G. H. Cady. 1915. 

Twenty-five cents. 

Bulletin 11. Coal Resources of District VII (Counties listed in Bulletin 4), by 

Fred H. Kay. 1915. None available. 

Bulletin 12. Coal Mining Practice in District IV (Mines in bed 5 in Cass, DeWitt, 
Fulton, Knox, Logan, Macon, Mason, McLean, Menard, Peoria, Sangamon, Schuyler, Taze 
well, and Woodford counties), by S. O. Andros. 1915. Free upon request. 

Bulletin 13. Coal Mining in Illinois, by S. O. Andros. 1915. Free upon request. 

Bulletin 14. Coal Resources of District VIII (Danville), by Fred H. Kay and K 

D. White. 1915. Postage four cents. 

Bulletin 15. Coal Resources of District VI, by G. H. Cady. 1916. Fifteen cents. 

Bulletin 16. Coal Resources of District II, by G. H. Cady. 1917. Fifteen cents. 

Bulletin 17. Surface Subsidence in Illinois Resulting from Coal Mining, by L. E. 
Young. 1916. Mailing weight, one pound. 

Bulletin 18. Tests on Clay Materials Available in Illinois Coal Mines, by R. T. 

Stull and R. K. Hursh. 1917. Mailing weight, one pound. 

Bulletin 20. Carbonization of Illinois Coals in Inclined Gas Retorts, by F. K. 
Ovitz. 1918. Postage two cents. 

Bulletin 21. The Manufacture of Retort Coal-Gas in the Central States, Using 
Low-Sulphur Coal from Illinois, Indiana, and Western Kentucky, by W. A. Dunkley and 
W. W. Odell. 1918. Postage two cents. 

Bulletin 22. Water-Gas Manufacture with Central District Bituminous Coals as 
Generator Fuel, by W. W. Odell and W. A. Dunkley. 1918. Postage two cents. 

Bulletin 23. Mines Producing Low-Sulphur Coal in the Central District, by G. H. 
Cady. 1919. Postage two cents. 

Bulletin 24. Water-Gas Operating Methods with Central District Bituminous Coals 
as Generator Fuel, by W. A. Dunkley and W. W. Odell. 1919. Postage two cents. 



76 PUBLICATIONS OF THE ILLINOIS COAL MINING INVESTIGATIONS 


*Bulletin 72. U. S. Bureau of Mines, Occurrence of Explosive Gases in Coal Mines, 
by N. H. Darton. 1915. Thirty-five cents. 

*Bulletin 83. U. S. Bureau of Mines, The Humidity of Mine Air, by K. Y. Williams. 
1914. Ten cents. 


^Bulletin 99. U. S. Bureau of Mines, Mine Ventilation Stoppings, by R. Y. Williams 
1915. 

* Bulletin 102. U. S. Bureau of Mines, The Inflammability of Illinois Coal Dusts, 
by J. K. Clement and L, A. Scholl, Jr. 1916. 


^Bulletin 137. U. S. Bureau of Mines, The Use of Permissible Explosives in the 
Coal Mines of Illinois, by James R. Fleming and John W. Koster. 1917. 

*Bulletin 138. U. S. Bureau of Mines, Coking of Illinois Coals, by F. K. Ovitz. 1917. 
Twenty cents. 


Bulletin 91. Engineering Experiment Station, University of Illinois, Subsidence 
Resulting from Mining, by L. E. Young and H. H. Stoek. 1916. None available. 

Bulletin 100. Engineering Experiment Station, University of Illinois, The Percent- • 
age of Extraction of Bituminous Coal, with Special Reference to Illinois ConditionSj by C. 
M. Young. 1917. Free upon request. 

Bulletin 113. Engineering Experiment Station, University of Illinois, Panel System 
of Coal Mining, A Graphical Study of Percentages of Extraction, by C. M. Young. 1919. Free 
upon reqtcest. 


* Copies may be obtained by addressing the Director, U. S. Bureau of Mines, Washington, 

D. C. 



THE UNIVERSITY OF ILLINOIS 
THE STATE UNIVERSITY 
Urbana 

Edmund J. James, Ph.D., LL.D., President 


THE UNIVERSITY INCLUDES THE FOLLOWING DEPARTMENTS; 

The Graduate School 

The College of Liberal Arts and Sciences (Ancient and Modern Languages and 
Literatures; History, Economics, Political Science, Sociology; Philosophy, 
Psychology, Education; Mathematics; Astronomy; Geology; Physics; Chem¬ 
istry; Botany, Zoology, Entomology; Physiology; Art and Design) 

The College of Commerce and Business Administration (General Business, Bank¬ 
ing, Insurance, Accountancy, Railway Administration, Foreign Commerce; 
Courses for Commercial Teachers and Commercial and Civic Secretaries) 
The College of Engineering (Architecture; Architectural, Ceramic, Civil, Electrical, 
Mechanical, Mining, Municipal and Sanitary, and Railway Engineering; 
General Engineering Physics) 

The College of Agriculture (Agronomy; Animal Husbandry; Dairy Husbandry; 
Horticulture and Landscape Gardening; Agricultural Extension; Teachers’ 
Course; Home Economics) 

The College of Law (three-year and four-years curriculums based on two years and 
one year of college work respectively) 

The College of Education 
The Curriculum in Journalism 

The Curriculums in Chemistry and Chemical Engineering 
The School of Railway Engineering and Administration 
The School of Music (four-year curriculum) 

The Library School (two-year curriculum for college graduates) 

The College of Medicine (in Chicago) 

The College of Dentistry (in Chicago) 

The School of Pharmacy (in Chicago; Ph. G. and Ph. C. curriculums) 

The Summer Session (eight weeks) 

Experiment Stations and Scientific Bureaus: U. S. Agricultural Experiment Sta¬ 
tion; Engineering Experiment Station; State Laboratory of Natural History; 
State Entomologist’s Office; Biological Experiment Station on Illinois River; 
State Water Survey; State Geological Survey; U. S. Bureau of Mines Experi¬ 
ment Station. 

The library collections contain (September 1, 1919) 442,539 volumes and 54,189 
pamphlets. 

For catalogs and information address 

THE REGISTRAR 

Urbana, Illinois 



\ 




